Research Paper - Energy Of The Future

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Founded 1905

THE NATIONAL UNIVERSITY of SINGAPORE Department of Mechanical Engineering

Energy: Past Practices & Future Directions

Done By:

Ang Chieh Sin Jaselin Chiang Hock Siong Hon Chia Jeng Kamarul Effendi Kingshuk Ghosh Lee Aik Ling Lim Wei Meng Loo Ming Yang Madhavan

995917N11

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1.0 Introduction Since the existence of mankind, different fuels have been depended upon as our sources of energy. Fossil fuels are instrumental in meeting the increasing energy demands of the global population with the main advantage of their easy availability at an affordable cost. Over the years, their relatively low prices have caused the problem of random usage. The question is, how long can this continue? With increasing consumption, it is only a matter of time before these resources are totally depleted.

That is not all. Pollution is another heavy price. Over the past few decades, the damage caused to the ecological balance can be attributed to the use of fossil fuels. This will present a grave picture for the future generations, unless their detrimental effects to the environment are checked soon. The question of sustainability of the environment is now a major concern. Environmentalists are concerned with the fact that Mother Nature can no longer take what we have been giving. Thus, there arises the need to explore usage of other sources of energy that will at the same time, satisfy our demands and inflict minimal harm to the environment. This is where the role of renewable energy sources becomes increasingly significant. Being the energy of the future, many countries had made major investments in these new energy sources, hoping to move away from the conventional dependence on fossil fuels.

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1.1.

Energy sources

The energy sources are divided into the renewable and non-renewable energy sources. The following two sections will describe briefly each group of energy sources.

1.1.1. Non- renewable energy sources These includes the fossil fuels namely coal, oil, natural gas as well as the non- fossil nuclear energy. Coal is mainly used in the iron and steel industries and approximately 37% of the electricity generated worldwide is produced from coal. Today, there is an estimate of total reserves of 984, 400 billion kilograms of coal, according to the BP Statistical Review of World Energy 2001. For oil, from its initial state of crude oil to its refined products like petroleum and diesel, are being widely used as a fuel in transportation, industries and domestic homes. The world has produced about 650 billion barrels of crude with another trillion barrels of proved reserves yet to be produced and an additional 10 trillion barrels of oil resources await development. Both coal and oil produce harmful pollutants upon usage unlike natural gas, which burns the cleanest. With its uses in heating, cooling and producing electricity and its outstanding environmental record, natural gas is a superior fuel in comparison with the other fossil fuels for the near and distant future. Nuclear energy is used in radioisotope production, nuclear medicine, and different types of advanced power reactor. Its benefits include its independence on the weather and non-emission of pollutants, but these are often weighed against the disadvantages of its high cost, waste disposal problem and nuclear weapon proliferation. For the major contributors of the above energy sources, refer to Appendix A.

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1.1.2. Renewable energy sources

This will include biomass, geothermal, solar, wind and hydropower. Biomass resources include wood, municipal solid waste, agricultural crops and other bio- products. It is used to provide heating and cooking in the residential sector and electricity in the industrial sector. It is the 4th largest energy source worldwide accounting for approximately 14% of total energy consumed (Refer to Appendix A) and the only non- renewable source that produce pollutants through burning. Geothermal energy is generated by the decay of radioactive isotopes of underground rocks and is stored in the Earth's interior. Its uses include agriculture, aquaculture, space heating and pasteurization of milk. One disadvantage is that its usage is only limited to places with strong tectonic activity (Refer to Appendix A for the main users of geothermal energy). Solar energy provides electricity through photovoltaic (PV) panels and might be the most promising renewable since they are found to be highly reliable, clean and silent, though its initial high capital cost may be too prohibitive. Wind energy, like solar, can provide a clean, abundant source of electricity. It has been the fastest growing energy technology for the past decade though there are disadvantages in instances where intermittency is a constraining factor and the chief expense of setting a turbine farm is too high. Hydopower makes use of the energy in flowing water to harness electricity. Refer to Appendix A for a detailed description of the generation of electricity. It also provides an option to store energy as well as to optimize electricity generation.

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1.2.

Trends in Production, Usage Pattern and Prices

In this chapter, the trends in the production, usage pattern and prices of the various fuels over the past years will be discussed along with its implications.

1.2.1. Trends in Production 160 140 120 100 80 60 40 20 0 1970

1975

1980

1985

1990

1995

2000

Year Coal

Natural Gas

Crude Oil

Nuclear Electric Power

Renewables

Figure 1.1: World energy production of the various non-renewable and renewable energy sources (1970-2000) Source: EIA, http://www.eia.doe.gov/emeu/aer/txt/tab1102.htm

From Figure 1.1, it can be seen that non-renewable energy sources dominate the scene, as compared to renewable ones. This is expected because non-renewables such as coal and oil has long been established as key sources of energy. Moreover, due to the nature of renewable energy sources that are usually capital intensive, a lot of countries are unwilling to turn to such alternatives. In addition, some of the drawbacks of these renewables also prevent their widespread usage. Crude oil is seen as the main component

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for the production of energy. Its trend is also the one with the most fluctuations due to its volatile nature as well as its sensitivity to issues in the political scene.

1.2.2. Trends in Consumption

45 40 35 30 25 20 15 10 5 0

Year Coal

Natural Gas

Crude Oil

Nuclear Power

Renewables

Figure 1.2: World energy consumption of the various non-renewable energy and renewable sources (1949-2000) Source: EIA, http://www.eia.doe.gov/emeu/aer/txt/tab1001.htm

Referring to Figure 1.2, crude oil is once again the leading component, followed by natural gas, then coal. Nuclear power and renewable energy sources are relatively insignificant when compared to the others. Coal was the leading source of energy in the middle of the 20th century. However, its position has gradually been taken over by the more popular crude oil that has a general rising trend from 1949 to 2000. Crude oil’s various fluctuations are caused by the political events like the sudden oil embargo imposed by OPEC in 1973 and the Iranian Revolution in 1978. Natural gas shares a similar trend with crude oil since these hydrocarbons are usually produced

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simultaneously. The small rate of increase of usage of nuclear energy is attributed to its many drawbacks, among them the potential damage to environment and the society and the problems posed by the disposal of its toxic wastes.

1.2.3. Trends in Population Growth

The production and consumption patterns are very much affected by trends in population growth. Population growth is one of the main factors leading to increased demand for energy. Population of the world continues to increase as time progresses. A major component of this population growth arise from the developing countries like China, India and the rest of Asia, as can be seen from Figure 1.3 below.

G l o b al p o p u la t i o n c o n t i n u e s t o ri s e 10 8 6 4 2 0 1950

1960

1970

A f ric a E ur o pe N o rt h A m e ric a

1980

1990

2000

2 0 10

2020

2030

2040

2050

A sia a n d O c e a n ia L ati n A m e ric a a n d C a ri b b e a n

Figure 1.3: Global Population Trend Source: http://www.wri.org/powerpoints/trends/sld002.htm

For more details on how population growth affects energy usage, refer to Appendix A.

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1.2.4. Prices of fossil fuels and comparison of costs with other commodities

The price trends of the fossil fuels over the past 30 years from 1970 to 2000 with 1996 as the base year for price comparison will be discussed. These trends will also be compared with those of some of our everyday commodities. The implications of such trends are also being discussed.

16

Coal

14

Natural Gas Crude Oil

12 10 8 6 4 2 0 1970

1975

1980

1985 Year

1990

1995

2000

Figure 1.4: Fossil fuels price trend from 1970- 2000 Source: Energy Information Administration

It is observed that crude oil has been the most expensive fuel, followed by natural gas, then coal. This is not unusual since oil has been the most dependable fuel in most industries with the widest applications and uses compared to natural gas and coal. As discussed earlier, the turbulent nature of the fluctuations in crude oil price at various peaks are caused by shortages due to the sudden oil embargo by OPEC, Iranian Revolution and Gulf War respectively in 1973, 1979 and 1990.

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Prices of natural gas have been relatively constant over the past 3 decades due to its low usage. However, with increasing emphasis placed on natural gas to replace oil as the dominant fossil fuel in part due to its cleanliness and relative abundance, there is a sharp increase in the prices of natural gas towards the end of the 20th century.

Coal is the most abundant resource among the three fossil fuels which half- explains for its lowest price. The reduced level of economic growth below expectations has affected demand for coal and the declining oil prices create keen competition, thus causing coal to maintain a relatively low price up till today.

On the whole, fossil fuel prices have been relatively low and more or less constant, as compared to other commodities in the market. Refer to Figure 1.5 below.

1.3

Sugar

1.2

Milk

1.1 1.0 0.9 0.8 0.7 0.6

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 Year

Figure 1.5: Commodities (Sugar and Milk) price trend from 1986- 1997 Source: U.S Department of Labor/ Bureau of Labour Statistics

It was observed that over the past few years, prices of other commodities like sugar and milk have been on a general increasing trend whereas the prices of the fossil fuels remained low when comparison is done in the same period of time and area.

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This forms a major incentive for fossil fuels usage, especially over the more expensive energy obtained from renewable technologies. It is particularly evident in developing nations where governments would be more concerned with economic progress by utilizing these relatively cheaper sources of energy rather than invest heavily in capitalintensive renewable technologies, even if all these are done at the expense of the environment.

1.3.

Impact of the energy fuels on the environment

Relatively cheap prices of the fossil fuels result in their excessive uses and ultimately result in wastage. Environmentalists are extremely concerned with the increasing concentration of greenhouse gases since the Industrial Revolution. Carbon emission is one of the major problems arising from fossil fuel usage. From Figure 1.6 below, it is shown that the global carbon dioxide emission levels have been increasing over the years. This is not surprising since the production and consumption of the fuels have been on an increasing trend as had been discussed earlier on. This effect is thus detrimental to our environment and our future generations to come and must be checked as soon as possible.

8000000 7000000 6000000 5000000 4000000 3000000 2000000 1000000 0

Year

Figure 1.6: Global carbon dioxide levels from fossil fuels burning (1786 – 2000) Source: World Climate News, Issue 21, June 2001

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1.4.

Future developments of energy

1.4.1. Non- renewable energy sources •

Coal

At current production levels, known coal reserves are forecasted to last over 200 years, which is significantly longer than the known reserves of oil or gas. Coal will continue to be an important source of primary energy and with new technology at hand, would ensure its importance well into the 2lst century. As a result of continually improving clean coal technologies, coal will be used more and more efficiently to meet the increasingly stringent environmental regulations in force worldwide.

•

Oil

Oil is estimated to run out in 60 years time considering present consumption rates. With its extensive usage, it is thought that no other resources could make oil redundant. Even if a revolutionary, new energy alternatives were discovered tomorrow, it would take up to 30 years, if not longer, to phase out existing oil- burning technologies and massive capital investments in oil supply systems. “Hubbert’s Peak” Theory states that the production of oil would follow a bell curve, and this may turn out to be true. The Saudis can dominate the whole oil market but they cannot offset a real shortage. It is also unlikely to see any drastic breakthroughs in technology that could significantly change oil supply. However, oppositions to this theory believed that with the recent additional discoveries, such as deep- water oil extracted in South Atlantic, as well as untapped reserves in Caspian Sea, Siberia and Africa, the outlook of oil could be changed considerably. Still, with global

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warming, this situation could lead to urgent but tentative reasons to pursue alternatives to oil. •

Natural gas

Concerns regarding acid rain and global warming will no doubt make natural gas look promising. The two areas that could lead to expanded use of natural gas are fuel cells used for generation of electricity (Refer to Appendix A for the advantages of fuel cells) and transportation, since it burns far cleaner than gasoline and diesel fuel. For the past decades, the price of natural gas has been rising more slowly and in a stable manner compared to oil. Furthermore, the inventory of natural gas is predicted to be 5 times more than crude oil. It is possible then that the use of natural gas might overwhelm the use of crude oil.

•

Nuclear energy

Despite the potential hazards imposed by nuclear energy, scientists have predicted that nuclear energy will still be in continuous use due to the huge amount of energy it can generate without pollution. Experts believed that many countries would be turning to nuclear power to power their lands in the near future. In the long run, it has to be noted that until more advanced and efficient disposal technologies were successfully implemented, the current costs of disposal, coupled with the capital intensive power plant set up and reactor maintenance costs, would be too high for the consumer or end-user to bear. Another aspect would be the limited fissionable reserves of Uranium-235, which would be costly to mine for in an exploration.

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1.4.2. Renewable energy sources •

Biomass Energy

Even though biomass provides a clean renewable energy source, its future will depend heavily on the efforts of both developed and developing nations to improve on the current biomass energy conversion efficiency. Dedicated energy crops have to be grown to meet the growing energy demand and the infrastructure of the developing nations needs to be improved to efficiently transport the bio-fuels. It is only then that the cost of biomass energy can be made competitive with the fossil fuels.

•

Geothermal Energy

The entire world resource base of geothermal energy has been calculated to be larger than the resource bases of coal, oil, gas and uranium combined. To fully exploit the potential of this huge source of energy, more funding into exploration and technological research has to take place. However, the geographical constraint that comes with the usage of geothermal energy implies that countries not located in areas of tectonic activity would be less likely to adopt this source as an alternative for the future.

•

Solar Energy

Its application in photovoltaics seems to have lots of room for improvement. PV cells are becoming gradually cheaper and highly mobile, allowing for electricity generation even in remote places. Its future lies in the technological advances to improve its efficiency, as well as the storage of the energy generated. Most experts believe that mass-marketed solar-propelled cars will not be realizable in our foreseeable future. However, it is

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possible that in 15 years, most cars will use some onboard solar-power generation system. Solar assistance will be important to sustaining long battery lives owing to the heavy drain of electrical energy by computer and security systems of the automobiles of the future. •

Wind Energy

Wind energy can be the most cost effective and clean source of electrical power. The major technological developments enabling wind power commercialization have already been made although there need to be infinite refinements and improvements. However, its main limitation is its intermittency that will result in a high level of uncertainty for all industrial and commercial applications. Still, the technology itself has leapt in recent years and special efforts must be in place to ensure that renewable energy technologies become a significant part of our energy picture in the next century. •

Hydropower

Hydropower has environmental impacts that are very different from those of fossil fuel power plants. The actual effects of dams and reservoirs on various ecosystems are only now being understood better. The future of hydro-electric power will depend on future demand for electricity, as well as how societies value the environmental impacts of hydro-electric power compared to the impacts of other sources of electricity.

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1.5.

Looking towards the future

The demand for energy will continue to grow. Economies are expanding, populations are growing and energy-intensive technologies are spreading. There is also an increasing global recognition of the environmental impacts of using non-renewable sources for energy production. Over time, we will have to continually reduce our dependence on fossil fuels and turn increasingly to the energy efficient, sustainable renewables.

One main disincentive of renewable energy sources is that such technologies are typically capital intensive. The setting up of the required infrastructure and the investment in technological research add up to a higher cost that will eventually be passed on to the end-user. However, some renewables are actually quite well-developed, owing to the low operating costs since the basic fuel is normally free or of low cost. Thus, the overall costs in the long run would somehow be justified. As such, renewable energy sources are still very much in the running as energy of the future.

The reliance on renewable energy sources, which arises from the realization of the environmental impacts of fossil fuels, also resulted from the sustainability of such sources. It is inevitable that fossil fuels will eventually run out with costs escalating exponentially. On the other hand, renewable energy is harnessed from the basic elements of the environment, such as water, sun, wind and earth energy. Thus, it would always be readily available provided the required infrastructure is up and running. However, the role of the government in establishing these infrastructures has to be an active one if renewable energy is to be part of our children’s future.

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2.0 Applications of Renewable Energy After identifying the different sources of energy, which are used to meet the everincreasing demands of the growing population, there are certain conclusions that we can come to. Firstly it is quite obvious that the energy needs are increasing very fast and it will be naive to expect any decline in this trend. Secondly we have seen that over the years this growing need has been met by fossil fuels like oil, coal and natural gas. Over the past few decades, the world has slowly realized the hazards that these energy sources pose to the environment, and are awakening to the calls of environmental activists. Nations have realized that the answer lies not in the cut down of usage, as that is practically impossible, but in the effective conservation of fossil fuels and increases reliance on renewable energy sources like solar energy, wind energy, hydropower etc. These energy sources, if harnessed properly are capable of meeting the energy needs, with little or no detrimental effect to the environment. Thus the future of the world energy demands lies in the proper utilization of renewable energy sources. In this section of the report, the main objective is to design a solar heating and electricity system for a remote resort. In the following pages, two systems will be introduced, first, a solar water heating system for the resort followed by the solar photovoltaic system to meet the electricity needs of the resort. Before introducing the two designs and their detailed specifications, it is important to introduce the design of the resort. Factors like location, size, accommodation etc have to be specified for a proper understanding of the energy needs, and their subsequent fulfillment.

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2.1.

Description of Resort

As mentioned earlier the resort is situated in a remote location. The immediate implication of this is that it is inaccessible to conventional energy sources like oil, natural gas and coal owing to transportation problems. The resort is located on an island off the coast of Singapore. This means that the weather is similar to that of Singapore, which enjoys tropical climate. The resort has an area of 40 00 square meters and can house up to 48 guests at any one time. The number of staff in the resort has been fixed at 12, thus giving a total figure of 60 residents in the resort. The layout of the resort is shown in Figure 2.1.

BLK 2

BLK 3

BLK 1

BARBECUE AREA

COMMON FACILITIES AREA

BLK 4

POO BLK 5

BLK 6

CHILDRENS PARK

Figure 2.1. Resort Layout The guests are accommodated in six blocks situated around the central facilities area. Each block has four chalets each on a twin-sharing basis. Each chalet is allocated with a

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washroom. Apart from the four chalets in each block, there is a maintenance room, which takes care of the storage of PV batteries and maintenance equipment. The chalets each have an area of 50 square meters and the maintenance room of 10 square meters, thus totaling an area of 210 square meters per block. The common facilities area houses the reception, main office and staff quarters. Apart from that it has dining facilities for the guests and multi purpose halls. There are also outdoor activity centers comprising of a swimming pool, golf driving range, children’s park, playgrounds, walkways and barbecue pits. All in all the resort is meant to provide the guests with a relaxing stay and an unforgettable enjoyable experience.

2.2.

Background Information

After getting an idea of the location and the design of the resort, the next important information is some of the technical specifications, which have been used in the calculation of the energy needs and in meeting them. First of all it is important to know how much solar irradiation the resort receives daily. This figure was found out to be 13.5 MJ / m 2. (Source: “Energy and Environment in the 21st Century”, M.N.A Hawlader 2001 Dec 26 – 28 ).

Next, assumptions were made on the temperature of the hot water that is to be supplied to the guests as well as the cold water from the main supply lines. The hot water temperature for the resort has been fixed at 60o Celsius and that of the cold water at 28o Celsius.

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These values are critical in calculating the energy requirements of the resort for the hot water supply, following which the daily requirements of hot water for each person is determined, and later found to be 40 liters of hot water per day (Source: “Solar Energy Systems Desig n” /1985, Norman C. Harris, Cydney E. Miller Irving E.Thomas).

The resort needs two systems to meet its energy requirements. The hot water needs are met by a direct solar thermal heating system. The second system is a Photovoltaic system, which supplies the remaining electricity needs and provides for water heating at night.

The next section covers the solar thermal water heating system in greater detail.

3.0 The Solar Thermal Water Heating System 3.1

Introduction

The solar thermal water heating system takes care of the hot water needs of the resort. The basic idea of the system is to utilize solar radiation from the sun to heat up the water. Solar collectors absorb the radiation, which utilizes the energy to heat up the water. This hot water is stored in thermal storage tanks, and is supplied to the residents as required. For this purpose, initially two systems were designed. The first design configuration is known as the semi-decentralized system in which solar collectors were mounted on the roof of each residential block and the common facilities area. The solar collectors on each residential block supply hot water to the chalets, while those on the common facilities area supplies hot water to the staff quarters.

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The second design configuration consists of a centralized system with just one set of solar collectors on top of the common facilities area. This would meet the hot water needs of the entire resort. Thus it is necessary for the hot water to be pumped to the different blocks for guest use.

After considering the pros and cons of both the systems, the semi-decentralized type was selected for the final design. There were certain disadvantages with the centralized system, among them is that: (i)

The centralized system required pumps to supply hot water to the guests in the residential blocks. This incurs additional costs.

(ii)

In the event of a breakdown of the system, the entire resort would be affected, since no backup is available. This is not the case for a semi-decentralized system, as only a certain part of the resort would be affected.

(iii)

Maintenance costs are much higher for a centralized system.

Keeping these reasons in mind, the semi-decentralized system was selected to meet the hot water needs of the resort.

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3.1.1. The Semi-Decentralized System

In this section the semi- decentralized system solar thermal heating system will be explained. Emphasis will be made on the working principles of the system, which is assisted by a schematic diagram. Next the various components of the system will be introduced together with their respective functions.

3.2.

Working Principle of Solar Thermal Water Heating System

As explained earlier, the semi-decentralized system is more practical in its usage particularly for a large resort as the one under consideration. A schematic of the system is shown in Figure 3.1. In the diagram the blue lines trace denotes the flow of cold water from the main supply lines, while the red lines denote the flow of the water after it is heated up to the required temperature of 60o Celsius.

As can be seen from the diagram the cold water enters to the storage tank through the supply lines. From the tank the cold water flows to the solar collector. As can be seen from the schematic diagram there is a differential controller, a check valve and an air vent in this section of the flow. The differential controller acts as an activation/deactivation device controlling flow of cold water into the solar collector. It is aided by the two temperature sensors. In the event that these sensors detect a temperature difference, the differential controller is activated, enabling flow of water into the solar collector for reheating. The two temperature sensors are ideally located at the point of exit of the hot

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water from the tank, and at the point where the water leaves the tank and flows into the solar collector. The check valve is added to the flow network, to prevent backflow of water into the storage tank. The air vent is a very important attachment, as it prevents any air bubbles from entering the solar collector. In the absence of an air vent, these bubbles will enter the collector and vaporize. Consequently, this affects the flow, as the water vapor exerts its own pressure, affecting the flow of water. Once the cold water enters the solar collector, it is heated up by the solar radiation that is absorbed by the collector. The area of the collector determines the temperature to which the water is heated, and the area in turn is determined through calculations, taking into account the irradiation form the sun. Once the water is heated up to the required temperature it flows back into the thermal storage tank. Along the way, it passes through a check valve and a shutoff valve. The check valve performs the same function, except that in this case, it now prevents backflow of the hot water into the collector. The shutoff valve is added to the system simply for maintenance purposes. In case of any fault to the system, the shutoff valve is activated, thus stopping flow from the collector to the tank. Thus, in this way, the heated water will find its way into the thermal storage tank. In the tank, the thermo-siphon process is utilized in which the cold water in the tank, being heavier, moves to the bottom of the tank. This in turn automatically forces the hot water to rise to the top of the tank. In this respect, the thermo-siphoning method is very useful, as it does not require pumps to maintain the flow of water. From the top of the tank the hot water exits into the piping network. Once the water leaves the tank it flows through an auxiliary heater. The function of the auxiliary heater is

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very important, particularly on days of insufficient sunlight, where the water might not be at the desired temperature of 60o Celsius, owing to the insufficient amount of solar irradiation. Thus the need to heat up this water to the desired temperature arises, and indeed this is the function of the auxiliary heater. Essentially, it is a normal water heater that is powered by photovoltaic cells. Thus even on days of insufficient sunlight, the guests are guaranteed hot water supply at 60o Celsius. The location of this auxiliary heater can also be changed to a point closer to the individual supplies to each of the chalets inside the block. This would be necessary in case there is a significant time difference between the supply of the hot water reaching the guests. After passing through the auxiliary heater, the water passes through an air vent and a pressure relief valve. The air vent as explained earlier, eliminates air bubbles trapped in the water. The pressure relief valve is a safety feature incorporated into the system. In such hot water systems, there is a chance of an excessive build-up of pressure in the piping network, which can be hazardous. Hence, there is a need to install a pressure relief valve in the system. In the case of excessive pressure build-up, the pressure relief valve is automatically activated, releasing the excessive pressure thus preventing any accidents. The next component in the system is the drain valve, which is used for maintenance purposes. Upon activation, this valve drains all the water from the piping network, enabling maintenance to be carried out on the system.

The next task is to channel the hot water into four separate networks to supply it to each of the four chalets in each block. A manifold takes care of this, and channels the water

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into the internal piping lines of the chalets. The water then finds its way into the taps in the washrooms in the chalets. Mixing valves are incorporated into these taps, which are used to mix the hot water (at 60o Celsius) and the cold-water form the supply line to get the water at the desired temperature.

As can be seen, the thermal water heating system design is an extensive one. Therefore, sufficient care has to be taken in incorporating components into the design, which will ensure safety and the need of maintenance of the system.

At night, the water is stored in the thermal storage tank and if required is also heated by the auxiliary heater. As mentioned earlier, in case the hot water takes a long time to reach the guests, the auxiliary heater can be shifted closer to the channeling point. Another option is to introduce a small loop in which the water in the pipes can flow back to the point of entry to the auxiliary heater, enabling the temperature of 60o Celsius to be reached quickly without much delay.

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3.3.

Determination of system requirements

The next step is to determine the requirements of the system. First of all, it is necessary to calculate the figures for hot water consumption of each block and the common facilities area. This figure is based on the fact that the daily hot water requirement in the resort is 40 liters per person. Once the volume of hot water required is determined, the next step involves the determination of the energy needs of the resort with regard to heating up the required amount of water to 60o Celsius. This value is obtained by applying the equations in Appendix B.

Based on the calculations, the following quantities for the blocks and the common facilities area are obtained.

Each Block

Common Facilities Area

Daily load (m3)

0.448

0.672

Daily energy consumption (MJ)

60.21

90.32

Area of collector required (m2)

7.81

11.72

Number of collectors required

3

5

Table 3.1: Results after Calculations

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3.4.

Individual Components

Having gone through the working principles of the solar thermal water heating system and the determination of the energy requirements, the next task is to select the various components. Of paramount importance are the solar collectors and the thermal storage tank, which will be discussed in greater detail.

3.4.1. The Solar Collector The solar collector is an integral part of the system as it traps the irradiation from the sun and transforms the solar energy into heat using an absorber. Insulated to prevent heat loss to the environment, its heat-transferring medium is generally a liquid; in this case, water is used. There are two main types of solar collectors available in the market: (i)

the flat plate type.

(ii)

the evacuated tube type.

For our design the flat plate type collector was selected. This is due to its higher performance to price ratio compared to evacuated tube types. Secondly flat plate type collectors provide a wider variety of mounting possibilities to the user. The next aspect of using the solar collectors is the mounting of the collector, with regards to its angle of inclination. As a rule of thumb, collectors in the Northern hemisphere face the South and vice versa. Another guide with regards to the inclination angle states that for optimum performance, the angle of inclination should be determined by adding 10 o to the latitude of the location concerned.

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(Source: “Solar Design Components, Systems, Economics” / 1989, Jan F. Kreider, Charles J. Hoogendoorn, Frank Kreith)

Here it should be noted that, the inclination angle could be varied from 10 o to 15o, without affecting the performance of the solar collector.

Taking these rules into consideration, the angle of inclination of the solar collectors was determined. As Singapore has a longitude of 103 º 50’ E and a latitude: 1º 18’ N, the inclination of the collector was fixed at an angle of 10 º facing South.

The next important aspect regarding the solar collectors concerns the arrangement of the collectors itself. It is very essential to look into this whenever the system requires the functioning of more than one collector. For our design, the Parallel Flow (with Reverse Return Header) type of collector the arrangement chosen is as shown in Figure 3.2. Reverse-return Return header

Collectors

Supply header

Figure 3.2: Collector Array Arrangement

As can be seen from Figure 3.2, the total length of supply piping and return piping to each collector is the same with this arrangement, and the pressure drop through each

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collector is theoretically equal, since the pressure drop through each collector is the same and the path length of the manifold piping for each collector is the same. This design thus ensures the same flow of water to all the collectors, without the need of any balancing valves or orifices.

Finally, the mounting of the solar collectors is decided. In this case, mounting kits are readily available in the market, certain factors must be considered while selecting a particular brand of mounting kit. Firstly, the mounting kit should provide flexibility in terms of the required angle of inclination. This would mean that the length of the tilt leg of the mounting structure had to be adjustable. Secondly, the mounting kit should also be properly insulated and should not be easily corroded or worn out.

3.4.2. The Thermal Storage Tank The thermal storage tank stores the hot water in the system until it is used. It serves as a medium to overcome the time difference between absorbing solar radiation and hot water consumption.

As a rule of thumb, the capacity of the tank should be such that it can store from 1.25 – 1.6 times the hot water requirements (Source: “Solar Energy Systems Desig n” /1985, Norman C. Harris, Cydney E. Miller Irving E.Thomas). For our case, this factor was fixed at 1.4 times the

requirement.

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3.5.

Selection of Components

3.5.1. Selection of Solar Collector Once the requirements of the system are known, a particular brand of solar collector is selected based on the efficiency, performance, price, area and resistance to atmospheric corrosion. An extensive survey was conducted of the various brands available in the market, and the choice was narrowed down to a few (Refer to Table 3.2). Model of Collector

Area (m2)

Unit Cost(US$)

Efficiency

MJ/m2 $

SolarStar SSC-32

2.724

754

0.612

0.01095

SolarStar SSP-32

2.724

690

0.571

0.01117

Imperial IP-32

2.750

627

0.571

0.01229

Imperial IC-32

2.750

700

0.612

0.01180

Empire EP-32

2.750

541

0.571

0.01425

Empire EC-32

2.750

627

0.612

0.01317

Radco 408C-HP

2.806

750

0.661

0.01190

Radco 408P-HP

2.806

608

0.588

0.01306

Table 3.2: Selection of Solar Collector

These choices were based on the parameters stated earlier. For each collector, the efficiency was determined through calculations, and then compared along with their respective prices as the basis of selection. Refer to Appendix B for the relevant calculations.

The final selection was made from the narrowed down list (the highlighted brand in Table 3.2). The main reason for choosing the SolarStar SSP-32 model of collector was its excellent anti corrosion feature. This model is specially designed for coastal waterfront

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locations where there is constant exposure to salt spray. Though other models possessed comparatively higher efficiency and performance values, the anti corrosion feature of SolarStar SSP-32 gave it an edge over the others. With such features, it will definitely have a longer life, thus saving a lot on replacements costs in the future.

3.5.2. Selection of Thermal Water Storage Tanks The first step in the selection of the thermal storage tank is the capacity of the tank. From calculations (refer to Appendix B), based on a daily requirement of 40 liters of hot water per person, the required capacity of the tanks was determined. A factor of 1.4 was multiplied to this value. For the final required capacities of the thermal storage tanks, please refer to Table 3.3 below.

Capacity of Storage Tank required Cost of SRS Storage Tanks (per tank)

Each Block

Common Area

0.454 m 3 (120 gallons)

0.795 m3 (210 gallons)

US$ 1275

US$ 1490

Table 3.3: Selection of Thermal Storage Tank

After determining the required capacity of the tanks, a particular brand was selected. As in the normal practice, a few parameters were considered, which were price, insulation properties and lifetime. After conducting extensive research on the main brands available in the market, the choice was narrowed down to the SRS brand of storage tanks. The main features of the SRS storage tanks are listed below: •

The tank walls are 0.076m (3inch) EPS (Expanded Poly Styrene) sandwiched between embossed aluminum with baked enamel finish.

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•

The frame is thermally insulated aluminum extrusions with baked enamel finish.

•

The tank has stainless steel fasteners, which adds to the life of the tank.

•

The tank comes with a partitioned lid, which gives easy access to all components during maintenance.

•

3.6.

All products come with a 20-year warranty.

Cost Analysis of Solar Thermal Water Heating System

Below is a list of the various components of the system with their unit prices. Solar Collector

- Suitable for coastal

US $ 690.00

waterfront locations

Thermal Storage Tank

- Excellent insulation

US $ 1275.00

- 20 year warranty

US $ 1490.00

Differential Controller

- Maintains uniform temperature of water in tank

US $ 117.00

Drain Valve

- For maintenance purposes

US $ 3.95

Check Valve

- Prevents backflow of water

US $ 10.29

Pressure Relief Valve

- Safety feature

US $ 11.00

- Releases excess pressure

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Mixing Valve

- Regulates hot and cold US $ 82.00 water automatically using bimetallic spring.

Mounting Kit

- Model used:

US $ 48.00

MTG-E-000 SolarStrut

- Tilt leg length 0.48m – 1.52m

Auxiliary Heater

- Activated by temperature sensors

US $ 118.00

- Runs on PV batteries Table 3.4: List of various components in system

The cost of the system for each block is calculated taking the quantities of the various components into consideration, as shown in Table 3.5. Each block Units

Unit Cost(US Dollar)

Total cost(US$)

Solar Collector

3

690.00

2070.00

SRS Storage Tanks

1

1275.00

1275.00

Differential Controller

1

117.00

117.00

Isolation (Drain) Valve

1

3.95

3.95

Check Valve

2

10.29

20.58

Pressure Relief Valve

1

11.00

11.00

Mixing Valve

4

82.00

328.00

Mounting Panel Auxiliary Heater

3 1

48.00 118.00

144.00 118.00

Piping Cost

-

168.00

168.00

Total

US$ 4255.53 Table 3.5: Price for each Block

In a similar way, the cost of the solar thermal water heating system for the common facilities area is also calculated, as shown in Table 3.6.

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Common facilities area Units Needed Solar Collector SRS Storage Tanks Differential Controller Isolation (Drain) Valve Check Valve Pressure Relief Valve Mixing Valve Mounting Panel Auxiliary Heater Piping Cost

5 1 1 1 2 1 6 5 1 -

Unit Cost (US Dollar) 690.00 1490.00 117.00 3.95 10.29 11.00 82.00 48.00 122.00 252.00

Total

Total Cost(US$) 3450.00 1490.00 117.00 3.95 20.58 11.00 492.00 240.00 122.00 252.00 US$ 6198.53

Table 3.6: Price for Common Facilities Area For piping costs please refer to Appendix B. The cost per block is then multiplied by a factor of six, to give the cost of all the blocks. Thus the cost for the 6 blocks is: 6 x US $ 4,255.53

=

US $ 25,533.18

The overall cost of the entire solar thermal water heating system is: US $ 25,533.18 + US $ 6,198.53 =

US $ 31,731.71

=

S $ 55,530.00

As can be seen, the solar thermal water heating system costs around S $ 55,000. As with all other renewable energy sources, there is a need of a higher initial capital investment. However, when viewed on a long-term basis, this would not be so if it were compared to a conventional fossil fuel system. The main reasons for this are that this solar thermal water heating system does not involve any fuel costs, as solar energy is free and abundant. The operating costs for this system is also comparatively lower than a fossil fuel system.

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Additionally, this system is also environmentally friendly. With practically no pollution to the environment, it is indeed an excellent choice for this particular application. It is hoped that with the help of government subsidies in the form of incentives such as tax exemptions, such systems would be more feasible and consequently return high benefits in the long run.

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4.0 Solar Photovoltaic Electricity Generation System 4.1.

Introduction

Solar radiation can be converted directly into electricity by using solar photovoltaic cells, which are commonly known as PV cells. Photovoltaic technology involves the interaction of the electrons freed by the sunlight with certain semi-conductor materials, such as Silicon, in the PV cells. Energy from the sun is radiated in the form of discrete packets of electromagnetic radiation known as photons. Each photon possesses energy according to the formula E =

hc where h is the Planck constant (6.626 x 10-34 Js); c is the speed of λ

light (3 x 108 m/s) and λ is the wavelength of sunlight. Sunlight composed of photons with wavelengths in the range of 0.3 to 3 µm. When a photon delivers its energy to the PV cells, electrons flow towards one terminal of the semiconductor, creating a negative charge, while the terminal that emits the electrons is positively charged. If a circuit is connected across both terminals, a direct current (DC) forms and electrical energy can be delivered to an external load.

There are numerous benefits for a solar photovoltaic system. A solar PV system can last for about 30 years since the PV cells are reliable and durable. Little maintenance is required since there are no moving components like turbines, pumps and this keeps the cost of maintenance low. One of the most significant advantages is that a solar PV system utilizes energy from the sun, which is totally free and environmental friendly. Moreover

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the PV cells can be used in remote locations for generation of electricity and this serves our objectives of this design project. A PV system is versatile and can combine with other types of electric generators to charge batteries and provide power on demand.

4.2.

Working Principle of Solar Photovoltaic System

In this application, the solar photovoltaic (PV) system is used for generation of electricity for the entire remote resort. Refer to Appendix C for details on calculations for electricity consumption values for the entire resort. A semi-decentralized system comprising of a set of solar photovoltaic arrays for each block and the central facilities area has been adopted. This arrangement is similar to the configuration of the solar thermal water heating system. Industrial-grade cables link electrically from the power distribution outlets of the central main facilities area to the 6 residential blocks. Thus, in any unforeseen event that the batteries or direct solar irradiation are insufficient to meet the demands of any residential block, the affected block will be able to draw electricity directly from the power generated or stored in the central facilities area. A basic PV system consists of solar PV arrays and “Balance of System” (B.O.S) components: deep-cycle batteries and chargers, inverters, charge controllers, AC distribution panels. Figure 4.1 shows a schematic circuit diagram of the solar PV system.

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Figure 4.1: Schematic Diagram of PV System

During daytime, two processes are taking place concurrently as shown by the red lines in Figure 4.1 above. As solar radiation strikes the PV arrays, a potential difference will be generated between the electrical terminals of each array. Due to photoelectric effect, current will start to flow from the arrays to charge up the deep-cycle batteries, with regulation by the charge controllers to prevent overcharging of the batteries. At the same time, the charge controllers will also be transmitting the direct current (DC) generated by the PV arrays to the inverters for conversion to alternating current (AC) before distribution to the load. The power quality in Singapore is 240V and 50Hz. Therefore,

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electricity generated during daytime is both stored in the batteries and transmitted to the AC distribution panels for ready use. At night, the batteries will start to discharge electricity as shown by the blue lines in Figure 4.1 above. The charge controllers monitor the discharge process to prevent the batteries damaging from excessively rapid discharge. The DC from the batteries will then flow to the inverters to be converted to AC. In addition, the charge controllers, fused disconnected switch and surge protector will prevent the back flow of current towards the PV arrays, avoiding any damage to the PV arrays. The discharging process also takes place during prolonged periods of cloudy weather or erratic changes in meteorological conditions, defined as days of autonomy, which has been pegged at 3 days. This is quite a good approximation considering that the resort is located in Singapore, a sunny and tropical climatic region. Based on this design of the PV system, PV arrays and the other components must be selected carefully and thoroughly such that the PV system will be cost-effective. Selection criteria for all the components of the PV system will be presented in the next section.

4.3.

Individual Components

A solar photovoltaic (PV) system requires the following components: solar PV arrays, deep-cycle batteries and chargers, inverters and charge controllers to generate electricity efficiently. Each of these components has specific vital functions to ensure that the PV system operates effectively.

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4.3.1 Solar PV Modules The basic building block of PV technology is the single PV cells. Many PV cells are wired together and connected electrically to form a PV module, which in turn, collectively form a single PV array. The module is the smallest PV unit that can be used to generate substantial amounts of PV power, and are manufactured with varying electrical outputs ranging from about 10 watts to 300 watts of direct current (DC) electricity. The modules can then be connected into PV arrays for powering a wide variety of electrical equipment . There are 2 primary types of PV modules available commercially, the crystalline Silicon type, which can classified as either a single crystal (monocrystalline), polycrystalline or thin film. The single crystal PV module has the highest efficiency in terms of electrical output. It has a sunlight- to- electricity conversion rate of 12% to 15%, followed by the polycrystalline type and finally the thin film type being the lowest. Due to its high efficiency comparative to the other types of PV modules, single crystal PV module is therefore the most expensive to manufacture. Their cost per watt is S$12 comparing to $11 and $9 for polycrystalline and thin film respectively.

In addition to the PV modules, the components needed to complete a PV system include the Balance-of-System (BOS) equipments such as charge controllers, batteries, inverters, AC distribution panels, safety disconnects, mounting structure and cables.

4.3.2 Mounting Structure

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A mounting structure is required to support the solar PV arrays so that the modules are able to capture the maximum amount of sunlight. Thus, a mounting structure must be made of metal to provide the strength, rigidity and durability needed for support. It must also be light since the structure will be placed on top of the roof. With an adjustable tilt angle facility, the angle of the structure can be adjusted easily to suit the inclination of sunlight with respect to the roof.

4.3.3 Charge Controllers Charge controllers act as a voltage regulator to regulate the flow of electricity from the PV modules to the batteries and the load. The controllers keep the batteries fully charged without overcharging it. When the load is drawing power, the controllers allow charge to flow from the modules into the batteries, the load, or both. Upon detecting that the batteries are fully charged, the controllers stop the flow of charge from the modules. If the controllers detect that the loads have taken too much electricity from the batteries, it will disconnect the current flow until sufficient charge is restored to the batteries. This can greatly extend the battery's lifetime. Another important feature of charge controllers is that they block reverse current. PV modules work by pumping current through the batteries in one direction. At night, the modules may pass a bit of current in the reverse direction, causing a slight discharge from the batteries. In most charge controllers, charge current passes through a transistor, which acts like a valve to control the current. The transistor allows current to pass in only one direction and prevents reverse current without any extra effort or cost. In some charge controllers, an electromagnetic coil acts as a relay that opens and closes a mechanical switch. In this case, the switches open at night in order to block reverse current.

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4.3.4 Batteries The batteries store electricity for use at night or for meeting loads during the day when the PV modules are not generating sufficient power to meet load requirements. A solar PV system requires lead-acid, deep- cycle batteries to provide electricity over long periods as they are designed to gradually discharge and recharge 80% of their capacity hundreds of times, as opposed to the ones used in automobiles.

4.3.5 Inverters Alternating current (AC) systems require inverters to convert the direct current (DC) electricity produced by PV modules and stored in batteries into AC electricity. Different types of inverters produce a different quality of electricity. Power quality required by the loads must be matched with the power quality produced by the inverter.

4.4.

Selection of Components

Selection of the individual components depends on a few common criteria, namely the efficiency, power output, price of the components, size and their suitability for usage in Singapore.

4.4.1 Selection of Solar PV Arrays Solar photovoltaic (PV) arrays are selected based on the power generated by the modules. As can be seen from Table 4.1, BP5170S has the highest rated maximum power output of

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170W as well as a competitive efficiency compared to other brands but at a lower price. Thus, it is particularly suited for applications that need maximum power energy generation from a fixed array area. Its large 72-cell design and electrical output via quickconnect polarized DC connectors require fewer mounting structures and enable speedy installation. Figure 4.2 shows a diagram of BP5170S PV array.

Brand

Airtherm AT 100

Tech

Single Crystal

Alfasolar 120 M

Price/Watt (S$)

P (W)

L (mm)

W (mm)

ç

Price (S$)

100

565

1250

14.15%

953.80

120

660

1315

13.82%

1302.2

10.846

Panel Area (m2)

0.7063

0.8679

Kyocera KC125 G-2

Polycrystalline

125

652

1425

13.45%

1203.1

9.622

Axitec AC165P

Polycrystalline

165

795

1576

13.16%

1559.25

9.435

1.2529

Thin Film

58

920

920

6.85%

386.512

6.664

0.8464

Single Crystal

170

790

1595

13.49%

1560.5

9.163

1.26005

BP BP5170S

Table 4.1: Brands of PV arrays

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Figure 4.2: Diagram of BP5170S Solar PV Array

4.4.2 Selection of Mounting Structure Unirac roof racks U-GR/64 from “FORDS MTM” are selected as the mounting structure for the PV arrays as it has universal applications and fit all PV modules in the market and most importantly it is compatible with our choice of solar PV arrays. One important feature which makes Unirac roof racks stand out among the other commercial mounting structures is the adjustable legs to optimize the position of the PV arrays for absorption of sunlight throughout the year. Since the roof racks are manufactured of aluminium and galvanized materials, they are able to withstand corrosion under adverse conditions. As can be seen from Table 4.2, Unirac offers the cheapest price with the same housing capacity of PV arrays compared to other brands. Unirac roof racks are also used for mounting solar collectors for the solar thermal system. Figure 4.3 shows a diagram of a Unirac roof rack. Housing Price per Capacity unit (S$)

Brand

Model

Unirac

U-GR/64

2

280.5

2 Seas

UNI-GR/03

2

312.8

Zomeworks

UTR085

2

613.7

Table 4.2: Brands of Mounting Structure

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Figure 4.3: Diagram of Unirac Roof Rack

4.4.3 Selection of Charge Controllers PSC804 series charge controller from “DIRECTPOWER & WATER” is selected among all series because it gives the highest ampere capacity, as can be seen from Table 4.3 PSC804 is also cheapest among all other series after taking into account the quantity of charge controllers required for the PV system. PSC800 series is chosen because it is ideal for large residential photovoltaic system, has remote battery voltage sensing system incorporated into it as well as built-in surge protection. Figure 4.4 shows the diagram of the 800 series charge controller.

Model

Voltage V

Capacity A

Price per unit (S$)

Qty Total Price required (S$)

PSC 120

12

120

1128.75

156

176085

PSC 500

12

180

2441.25

104

253890

PSC804

12

360

2791.25

58

161893

PSC844

12

360

3316.25

58

192343

Table 4.3: Charge Controller Series

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Figure 4.4: DirectPower’s 800 Series Charge Controller 4.4.4 Selection of Batteries Correct battery selection is critical in the reliability of the solar PV system. One of the most important considerations in the selection of a suitable battery is the ampere-hour capacity and its relationship to daily depth of discharge (D.O.D). A solar PV system has to be sized to store a sufficient amount of power in the batteries to meet power demand during several days of cloudy weather, defined earlier as “days of autonomy”. All the batteries from “ENERGYSTORE” are flooded lead acid batteries designed for remote areas with high charging efficiency of 80%. They have a long life of 2500 cycle life to 50% D.O.D and require little maintenance. Referring to Table 4.4, the 12RP830 model is selected due to its relatively high-energy output, coupled with the lowest total cost taking into account the quantity of batteries required for the PV system. 12RP830 series batteries have a size of 0.501m x 0.233m x 0.570m and weigh 210kg that allows easy transportation and assembly. Figure 4.5 shows a picture of a battery from ENERGYSTORE.

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Price per unit (S$) 21.84 1400 9.96 481.25 8.64 463.75 8.04 462 6.84 427.5 6.48 437.5 5.46 341.25 Table 4.4: Batteries Series

Model Capacity Ahr Voltage V Energy KJ 24RP910 12RP830 8RP1080 12RP670 12RP570 6RP1080 6RP910

24 12 8 12 12 6 6

910 830 1080 670 570 1080 910

Qty required Total Price (S$) 116 258 292 314 369 389 461

162400 124163 135415 145068 157748 170188 157317

Figure 4.5: The Selected Battery

4.4.5 Selection of Inverters The selection for inverters is based most importantly on the Singapore power quality. The power quality of the inverters must be matched by the power quality of the load. The inverters also must match incoming DC voltage from the batteries. In our solar PV system, 12V batteries are being used; therefore the inverter must also read in an input voltage of 12V. Thus the Cherokee Titanium Series inverter from “MAYASOLAR” is ideal as it fulfils these two criteria, and has an optimum operating efficiency of 90%. However, from Table 4.5, the TS1000 series is selected because it has a relatively high output power of 1000W at the cheapest rate of all series considering the quantity of the

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inverters needed. A photograph of Cherokee Titanium Series inverter is shown in Figure 4.6.

Table 4.5: Cherokee Titanium Series Inverter

MODEL

Output Power

Qty required

Price per unit (S$)

TS150 TS300 TS500 TS1000 TS1500

150 300 500 1000 1500

1495 748 453 227 150

198.60 291.45 475.00 945.00 1,501.70

Figure 4.6: The Cherokee Titanium Series Inverter

Total Price (S$) 296910 218000 215175 214515 225260

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4.5.

Cost Analysis of Photovoltaic System

Component

Unit Price (S$)

Qty

Total Price (S$)

PV arrays

1,560.50

1,319

2,058,299.50

Batteries

481.25

258

124,162.50

Inverters

945.00

227

214,515.00

Charge controllers

2,791.25

58

161,892.50

Mounting

280.50

660

185,130.00

Total cabling

46 per metre

400

184,00.00

TOTAL COST (Initial investment cost)

2,762,400.00

Cabling 1% Mounting 7%

PV arrays

Charge controllers 6%

Batteries

Inverters 8%

Inverters

Batteries 4%

Charge controllers Mounting Cabling PV arrays 74%

Figure 4.7: Contribution of Individual Components to total cost

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It can be observed from Figure 4.7 that solar PV arrays attributed to majority of the initial investment cost of the PV system (75%). The current efficiency of a solar PV module is around 14%, which is rather low, and improvements are ongoing to increase its efficiency rate. Despite the high initial investment cost of the PV system, a PV system has low maintenance cost and is pollution free. It is hope that in the long run, advanced technology could improve efficiency of the PV arrays, thus reducing cost. In the mean time, it is still very much capital-intensive without government subsidy.

4.6.

Conclusion

It is clear as can be observed from the total cost analysis, owing to the costly initial investment of the entire purely photovoltaic system, it is extremely crucial for the government to play a more active role in introducing attractive incentives for projects involving the implementation of solar and renewable energy systems. Based on the energy consumption that has been determined for this resort, an alternative to consider is to use a hybrid system where fossil fuels would be used in diesel generators to complement the photovoltaic part of the electricity generation system. Implementing such hybrid systems would definitely lower the initial capital investment as compared to a purely photovoltaic system. However, it has to be emphasized here that pollution arising from the process of burning diesel oil may not be acceptable in places where people intend to escape from the hustle and bustle of urban life and to enjoy the splendors of nature without any pollution or disturbing noise. This is where the various economic factors would be taken into consideration in a detailed discussion in Chapter 5.

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5.0 Analysis of Entire Solar System 5.1.

A Quantitative Approach to the economics of Solar Energy

After designing both the solar thermal and the solar PV system, it is important to have a method of calculation to evaluate the economic value of such a system against a conventional fuel oil system that utilizes boilers, furnaces, generators and turbines. Although restrictions are placed such that only solar energy is available for usage for this remote resort, this comparison will help to establish a better understanding of how viable a solar system is, compared to the conventional fuel oil system. The various methods of economic analysis include annualized life-cycle costs, payback period, internal rate of return and benefit-cost analysis. They essentially differ in the manner in which they relate costs and savings. Annualized life-cycle cost analysis sums the various costs incurred over the lifetime of a system, brought to present value, eventually arriving at the life-cycle cost per year. The payback period method evaluates the period of time that is expected to lapse for the cumulative savings to offset the investment costs. The internal rate of return method, meanwhile, gives the interest rate at a point in time when the savings are exactly equal to the costs. This interest rate reflects on the rate of return for the investment and it would be compared to the investor’s minimum acceptable rate of return to determine the feasibility of the investment. The benefit-cost analysis expresses savings as a ratio of costs, where a higher ratio reflects a more desirable situation where feasibility is greater.

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For this analysis, the annualized life-cycle cost analysis method would be adopted. The other methods are not being considered due to the following reasons. Firstly, some of the other methods do not take into account the lifetime of the system nor any future costs that will be incurred as time goes by, thus giving an incomprehensive evaluation. Secondly, it is not always straightforward to express benefits gained and certain costs incurred in monetary terms, leading to an inaccurate assessment.

5.1.1. Annualized Life-Cycle Cost Analysis In this method, initial as well as all future costs for the entire operational life of both the solar system and fuel oil system will be considered. The system with the lowest life-cycle cost per year is therefore more economical. The period considered for our analysis is the longest lifetime of a particular system, in this case, the 30-year solar system. The initial cost consists of the investment and installation costs. Governmental incentives in the form of subsidies, tax rebates and other concessions are taken into consideration to give the net initial costs that would be incurred. Also included are the annual costs required to keep the system operational as well as other variable overheads. Among these are the maintenance, operating, transportation, and fuel costs. Another important component included are the environmental penalties imposed for the emission of greenhouses gases. Finally, there is still the lump-sum replacement cost that are incurred after a specified number of years required to keep the system operational once the expected lifetime is up. This is normally expressed as a percentage of the initial setup costs, since a large part of the infrastructure would still remain and only the major components of the system would require replacement.

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In order to have a meaningful comparison, all the future costs and benefits have to be discounted to their equivalent value in today’s economy. This is known as their Present Worth (PW). This is to establish a more consistent and equitable basis for comparison. The two main factors to be considered for the PW calculations are the excess inflation (i) and the discount rate (d). Excess inflation is the rate of price increase of a component above, or below general inflation. Discount rate is the rate (relative to general inflation) at which money would increase in value if invested in a financial institution. Using i and d, discount factors can be calculated using the formulas stated in Appendix D. There are two types of discount factors, one for the calculation of single payment after a certain number of years (Pr) and another for the calculation of a recurring cost (Pa). The PW of all the future costs, obtained through multiplication by these discount factors, will be summed up to arrive at the overall life-cycle cost of the system. However, consideration must be given to the salvage value of any replacements made within the period of analysis, normally at the end of this period. For any replacements, unless its lifetime coincides with that of the period of analysis, there will be a residual value left at the end of the period of time being considered. For convenience, we shall assume a linear relationship for this salvage value with the number of years in use. As such, the total lifecycle cost of the system will be obtained after subtracting away this salvage value. To obtain the annualized life-cycle cost, this total cost has to be divided by the discount factor (Pa) for the number of years of analysis, in order to take into consideration changes in the value of money arising from inflation and changing interest rates. For this particular case, this factor is now known as the annualisation factor.

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For the calculations, the values of the initial capital investments are derived from the previous two chapters. As for the operation, maintenance, transportation, fuel, pollution penalties and replacement costs, as well as the governmental incentives, they are assumed values obtained from reliable sources and case studies from around the world, such are the values of i and d. Details of the calculations and these basic cost-and-benefit elements of the solar and fuel oil systems are explained in Appendix D.

Annualised Life-Cycle Cost or Life-Cycle Cost per year (S$) Solar Thermal Water System (with PV backup) Fuel Oil System equivalent

14,600

Solar PV (for all electricity needs)

Fuel Oil System 26,363 equivalent

183,109

175,860

Combined Solar 197,709 System Fuel Oil System equivalent 202,223

Table 5.1: Annualised life-cycle costs of the various systems According to Table 5.1, a solar thermal water system is significantly more economical than the fuel oil system whereas for a PV system, the balance swings the other way. A consequence of this is that when the two systems are combined for the whole resort’s hot water and electricity needs, it is slightly more economical than an equivalent fuel oil system. It should be emphasized here that these results arrived after a substantial government subsidy of 40 % of the initial capital investments. There are also uncertainties brought about by the dynamic nature of fuel prices and the magnitude of pollution penalties imposed by the government. This forms the basis for a discussion on the advantages of a solar system, which will be covered in the next section.

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5.2.

A Qualitative Analysis of the economics of Solar Energy

5.2.1. Introduction Photovoltaic power generation is a versatile technology that can be used for many applications. It is estimated that the Earth receives 6000 times more solar energy yearly than Man had consumed. Moreover, because sunlight is available everywhere to everyone, nations that build extensive PV infrastructures will be less vulnerable to changes attributable to volatile fossil fuel markets and any fossil fuel shortages.

5.2.2. Advantages of Solar Photovoltaic •

Good for Economy

Any nation that builds a PV industry will boost employment rates, export energy technology, keep energy dollars at home for further domestic investment, and finally reap the ancillary economic benefits of controlling a technology whose impact will reach well beyond energy. Presently, Singapore is not much of a player in the global PV market due to its dependence on natural gas from Malaysia and Indonesia. The gradual change from oil to natural gas for power generation is a positive move towards clean power generation. However, this may not solve the problem of Singapore’s energy sustainability in the long run. Natural gas, like other fossil fuels, is a finite resource. Prices will fluctuate due to political climate and furthermore, its long-term supply is indeed uncertain. As of 3rd Oct, 2002, crude oil prices soar to a peak of US$30.08 a barrel briefly after a suspected terror attack on a French-flagged tanker off Yemen, which raised tensions in the world market already fretting about the possibility of an assault by the

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United States on Iraq. Thus we need to diversify our energy sources to prevent our economy from being adversely affected by fossil fuels’ price fluctuations. Singapore is blessed with plentiful sunlight throughout the year and our resort could be a starting point where solar PV systems could be a serious alternative to fossil fuels. Even today, governments of different countries have set aside substantial investment in research and development of PV technologies as well as offer subsidies on capital investments, some even up to 50% or more for solar PV system. Even if the subsidies are not substantial, there can be other incentives like tax exemptions or tax subsidies. The global PV market is growing. In the last five years, it has grown at an annual rate of 20%, and experts predicted that a sustained growth rate of 25% is achievable. At such a growth rate, worldwide shipments would approach 18 billion watts per year by 2020, representing a direct PV market of about $27 billion and an indirect market of double the size. The earlier Singapore involves itself in the PV market and its technologies, the more economic benefits it will reap in the future. As mentioned earlier, this venture into the PV systems for the resort will also create jobs directly or indirectly for the people. This fact could be used as a potential leverage to convince the government to embark on such ventures.

•

Good for Our Environment

PV produces no greenhouse gases, so its use will help offset carbon dioxide emissions. Consequently, building a PV infrastructure will provide insurance against global warming and climate change. Whenever each kilowatt-hour of PV electricity replaces a kilowatt-hour of fossil fuel electricity, there is a reduction in CO2 emissions by as much

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as 90% (Markvart, 1994). Its use curtails air pollution, which produces acid rain, soil damage, plant and animal damage, as well as human respiratory ailments. •

High Reliability

Originally developed for use in powering space satellites and equipments, PV cells were found to be highly reliable, especially in instances where it is expensive, difficult, or in some cases, virtually impossible to carry out necessary repairs to the power supply units. To provide customers with an ambient environment free from the pollutions, we need to have a reliable system that can provide the necessary electricity needs, without the pollution. •

Low Operating Costs

PV cells harness the energy from sunlight to produce electricity; hence the fuel source is free. The cells also require very little maintenance and do not produce any noise that may be present in other systems in the process of generating electricity. •

Modularity

It is possible to construct a PV system tailored to any size based on energy requirements. Furthermore, the owner of a PV system also has the option to customize the size, ability to move the system whenever energy needs changes or arises. Most of these installations operate in remote locations where other means of obtaining electricity supply would be virtually unfeasible due to geographical or other constraints. •

Less Cabling

The PV systems of the resort are situated close to where the electricity is used, requiring much shorter power lines compared to the case if power is to be transmitted from the utility grids, which are typically located at considerable distances away from the end-

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user. This results in reduced power losses due to inherent cabling resistance over long distances in the power lines. In addition, the use of PV eliminates the need for a stepdown transformer from the utility line. Thus, less wiring and shorter power lines means lower costs, shorter construction time, and reduced regulating paperwork.

5.2.3 Energy Return on Investment of Photovoltaic Systems The degree to which a source can be considered sustainable can be conveniently termed the energy return on investment, where ROI = E out / E in, which represents the ratio of the energy produced by a source over its lifetime ( Eout ) to the energy required to obtain or produce the source ( Ein ). In other words, we require a certain amount of energy to harness energy. To illustrate this in a scenario, consider the following: in order to convert petroleum to a usable form, it must be found, drilled, pumped, transported, refined, and transported again. All these efforts require energy. For PVs, the ROI is presently estimated to be in the range of 4:1. Hence, each kilowatthour used to produce a PPV system will generate 4kWh. As efficiency improvements are made in the manufacture and operation of silicon and other emerging technologies, such as thin films, the energy ROI for PVs are expected to continue to increase in the future. Improvements in module efficiencies of the PV modules could substantially lower cost, as Table 5.2 illustrates. This increase in efficiency and lower module costs will definitely reduce the initial capital cost of solar PV systems, hence making it more economically viable.

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Year

Module Annual Price Sales (millions Module (dollars Efficiency (%) Sales (MW) ($/W) of dollars ) per square meter) 1997 14 84 3.15 $265 $441 2000 16 174 2.55 $444 $408 2005 17 433 1.97 $853 $335 2010 18 1,078 1.51 $1,628 $272 2020 19 6,678 0.90 $6,010 $171 2030 20 4,1437 0.53 $2,1914 $105 Table 5.2: Projections of Crystalline-Silicon Sales and Price 1997, and Projected for Selected Years, 2000-2030 Source: Alternative Energy Facts, Statistics, and Issues. Table 4.10 page 80 Author: Paula Berinstein, Oryx Press 2001

5.2.4 Public Sentiments

From the existence of “Environmental Voluntary Contracts between individuals and Industry” (Environmental Contracts, Eric W. Orts and Kurt Deketelaere,2001) which is in support of green electricity, it can be seen that public sentiments are encouraging and most are willing to pay more for renewable energies. Riding on these growing sentiments to do our part for our environment, as in the case for the resort that is using environmentally friendly energy from PV systems could prove to be a selling point to attract customers. The potential economic benefits of producing green products are reflected in a publication of poll results in The Economist:

A poll shows that some people will pay for green products. Respondents were asked if they have avoided or would consider avoiding a product for environmental reasons. Sixty percent said “yes: in the United States and 56% answered affirmatively in Mexico. When ask if they would pay a 10% premium for a greener cleaning product, two-thirds said “yes’ in Venezuela and half of those on China agreed strongly. Of course, though

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consumers may tell pollsters they will pay a premium, getting them to do so at shop may be more difficult. Firms seeking global markets may be wise to include green benefits in their products. Source: “How Green is Your Market.” The Economist, Jan. 8 2000,p. 66.

5.2.5 International Funding and New Initiatives Global Environment Facility (GEF) of World Bank grant funding to buy-down the costs of the technology. In the period 1992-97, PV projects valued at a total of $793 million were approved in India, Indonesia, Mauritius, the Philippines and Sri Lanka. The project pipelines for 1998-99 included PV projects in Argentina, Bennin, Brazil, Cape, Verde, China, Egypt and India totaling $466 million. The World Bank and regional development banks (e.g. the Asian Development Bank) also provides loans for economically and financially viable projects. There are also a number of market transformation or enablement initiatives that aim greatly to increase the penetration of PV markets. These illustrations highlight the point that investment in PV system is indeed promising and funds are readily available.

5.3

Conclusion

Initial investments cost is high but the good it will do for the environment, economy and support from the government and financial institutions, and the goodwill of potential customers make this investment attractive. Besides the maintenance cost is low, system reliability is high and PV system does not require any fuel that may face depletion and price fluctuation.