Zero Energy Building

ZERO ENERGY BUILDING

1.INTRODUCTION Human-induced global warming or climate change is one of the greatest long-term threats to human kind and most other species on the planet. It will increasingly affect most aspects of our daily lives. Whilst climatic fluctuations have always naturally occurred, the current levels of carbon dioxide in the atmosphere are unprecedented for the last 400,000 years. Resource consumption and global warming are intimately interlinked. It is possible to reduce the effects of global warming by changing behaviors, and more fundamentally by de-linking cultural beliefs concerning prosperity, resource consumption and economic growth that link growth with increased energy use. If we change the way in which we act and consume, we can have an immediate influence on the climate change through our basic everyday activities. One of the key areas of debate in zero energy building is over the balance between energy conservation and the use of renewable energy. To the majority of zero energy designers, the aim of zero energy building is not only to design a building that, on balance, uses zero energy, but one that also minimises all energy use, irrespective of the fact that that the energy may come from renewable resources.. However, while recognizing that energy conservation has a part to play, a sizeable body of designers consider that it is of lower importance and instead rely to a greater extent on 'active' techniques (solar power, wind turbines, etc.) to make up the energy / heat shortfall.

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2.HISTORY The ancient Greeks and Romans used solar design features in their housing, but the first zero energy building of the modern era were built in Germany after the first world war, when the Allies occupied the Ruhr area, including most of Germany's coal mines. These designs were studied in the United States, but had little influence on builders. The first consciously zero energy building in the US

[1]

was designed in 1940 by

George F. Keck for a Chicago area real estate developer named Howard Sloan. Keck had designed an all-glass house for the 1933 Century of Progress Exposition in Chicago and was surprised to find that it was warm inside on sunny winter days, even though the furnace hadn't been installed yet. Keck was not aware of the research being done elsewhere on solar architecture, but he gradually started incorporating more south-facing windows into his designs for other clients, and by 1940 he had learned enough to design a passive solar house for Sloan. Sloan built a number of zero energy building in the 1940s, and his publicity efforts influenced a number of other builders during the postwar housing boom (Sloan is also credited with popularizing the term "solar" to describe his houses). But some builders of that era didn't realize that the houses were designed to face south, and many were built facing other directions, which hurt their reputation. Critics also pointed out that windows and doors weren't always properly sealed. Public interest declined by 1950 due to cheap oil and general prosperity, until it was revived after the 1973 oil crisis. Edward Maria’s book 'The Passive Solar Energy Book' published in 1980, was an important milestone from which interest in this field developed.

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3. Development of Zero Energy Building The development of zero energy buildings has been made possible not only through the progress made in new construction technologies and techniques, but has also relied on academic research on traditional and experimental buildings in order to generate the data for the computer models. The zero energy building concept can be seen as a progression from other lowenergy building techniques. Amongst these, the Canadian R-2000 and the German passive house standards have been influential. Government and internationally sponsored demonstration projects such as the first super insulated Saskatchewan House, and the International Energy Agency's Task 13 have also played their part. And, in particular, the many enthusiastic private individuals who commissioned houses using cutting edge low energy technologies has been vital. For zero energy building to wide acceptance is likely to require government support or regulation, the development of recognized standards, or significant increases in the cost of energy.

Fig 3.1

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4.Design and Construction The design and construction methods which result in zero energy buildings appear to depart significantly from conventional building practice. Conventional designers and builders rarely do any energy analysis or lifecycle operating cost calculations on smaller buildings and appear to over-emphasize minimizing first costs . A competent ZEB designer is always interested in the lifecycle energy consumption effects of system options and is usually willing to increase first costs if they reduce energy demand and operating costs by an equal or greater amount. The ZEB approach might be described as energy first building design. In the ZEB approach every decision about major sub-system selection is evaluated in terms of its lifecycle energy demand consequence. To achieve minimal energy use, the design and construction of zero energy buildings departs significantly from conventional building practice. In conventional building design, the emphasis is normally on minimizing construction costs. Designers rarely do any energy analysis or lifecycle operating cost calculations beyond those necessary to comply with local building codes. In the ZEB approach, every decision about major sub-system selection is evaluated in terms of its future consequences on energy demand using life cycle energy analysis. ZEB designers are usually prepared to increase construction costs if doing so will reduce energy demand and operating costs by an equal or greater amount. The ZEB approach might be described as "energy first" building design. In addition to using renewable sources, zero energy buildings are also designed to make use of energy gained from other sources including white goods, lighting, and even body heat. They are normally optimized to use passive solar heat gain, use thermal mass to even out temperature variations throughout the day, and in most climates are super insulated.

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All the technologies needed to create zero energy buildings are available off the shelf today. Designers typically use sophisticated computer simulation tools to take into account a wide range of design variables such as building orientation (relative to the sun), window type and placement, overhang depth, insulation values of the building elements, air tightness, the efficiency of heating, lighting and other equipment, as well as local climate. These simulations help the designers to know how the building will perform before it is built, and enable them to model the financial implications on building cost.

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5.Techniques of Collection Zero energy building designs ordinarily use one or more of three techniques to assure solar gain: 1.

Direct Gain - where sunshine is allowed to pass directly through windows and/or skylights into the living spaces themselves, and to warm the air and surfaces there. A home with sun-facing windows and a high-mass floor is a short-cycle example of this and John Hait's "Passive Annual Heat Storage" (PAHS) method is an example of an annualized solar approach primarily using this path.

2.

Indirect Gain - Where sunlight strikes an intervening material (such as water or a solid mass behind glass), and then arrives at the living spaces indirectly, after being captured, stored and re-released by that material. Examples of this are Trombe walls, water walls and roof ponds. The Australian deep-cover earthed-roof, innovated by the Baggs family of architects, is an annualized example of this path.

3.

Isolated Gain - Here the solar heat is passively captured and stored in isolated places or devices and then only allowed to move passively into the actual living spaces when and if desired. Examples of this are partitioned away sun-spaces, greenhouses, "solar closets" and thermosyphon flat-plate collectors. Don Stephens' "Annualized GeoSolar" (AGS) heating is an annualized example of this option, which offers the advantages of preventing over-heating when living spaces are already deemed warm enough, and of extending time-delays until such heat will be desired.

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Direct and Indirect gain systems suffer because we have no reasonably priced transparent thermally insulating materials with R-values comparable to standard wall insulation. Aerogel is a promising, though expensive technology that might solve this. In practice the simplicity of isolated gain design, combined with the good long term performance and low cost make this the most practical method. To understand this design, consider a hypothetical house based on the work of Barra.

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6.Energy Generation In the case of individual houses, various Microgeneration technologies may be used to provide heat and electricity to the building, perhaps using solar cells or wind turbines for electricity, and bio fuels, or solar collectors linked to seasonal thermal stores, for space heating. To cope with fluctuations in demand, zero energy buildings are frequently connected to the electricity grid, and may export electricity to it when there is a surplus. Others may be fully autonomous buildings. Arguments for Microgeneration are: •

A significant proportion of electrical power is lost in the national grid (approximately 8% in the United Kingdom according to BBC Radio 4 Today Programme in March 2006). Microgeneration does not incur this loss.

•

Microgeneration reduces the transmission capacity requirement of the national grid, avoiding the need for additional grid upgrades.

•

By curbing the rising demand for grid electricity, Microgeneration can avert the need for investment in large new power stations.

•

Microgeneration can result in low or zero energy costs, particularly if surplus electricity can be sold to the national grid.

Bringing

energy

generation

closer

to

the

consumer

by

means

of

Microgeneration may have the further benefits of: •

Allowing individuals concerned about climate change to directly lower their carbon output.

•

Helping to overcome the antagonism of a minority towards large-scale renewable energy installations such as wind farms

Here are some example of Microgeneration with there work

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Photovoltaic cell-: Solar cells called photovoltaic made

from

thin

slices

crystalline

silicon,

arsenide,

or

semiconductor

of

gallium other materials

convert solar radiation directly into electricity. Fig 6.1 The PV cell consists of one or two layers of a semi conducting material, usually silicon. When light shines on the cell it creates an electric field across the layers, causing electricity to flow. By connecting large numbers of these cells into modules, the cost of photovoltaic electricity has been reduced to 20 to 30 cents per kilowatt-hour. Americans currently pay 6 to 7 cents per kilowatt-hour for conventionally generated electricity. The greater the intensity of the light, the greater the flow of electricity. PV systems generate no greenhouse gases, saving approximately 325kg of carbon dioxide emissions per year - adding up to about 8 tones over a system's lifetime - for each kilowatt peak (kWp - PV cells are referred to in terms of the amount of energy they generate in full sun light).

Solar PV and your home

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You can use PV systems for a building with a roof or wall that faces within 90 degrees of south, as long as no other buildings or large trees overshadow it. If the roof surface is in shadow for parts of the day, the output of the system decreases. Solar panels are not light and the roof must be strong enough to take their weight, especially

if

the

panel

is

placed

on

top

of

existing

tiles.

A trained and experienced installer should always carry out solar PV installations. Cost and maintenance Prices for PV systems vary, depending on the size of the system to be installed, type of PV cell used and the nature of the actual building on which the PV is mounted. The size of the system is dictated by the amount of electricity required. For the average domestic system, costs can be around £4,000- £9,000 per kWp installed, with most domestic systems usually between 1.5 and 2 kWp. Solar tiles cost more than conventional panels, and panels that are integrated into a roof are more expensive than those that sit on top. Grid connected systems require very little maintenance, generally limited to ensuring that the panels are kept relatively clean and that shade from trees has not become a problem. The wiring and components of the system should however be checked regularly by a qualified technician. Stand-alone systems, i.e. those not connected to the grid, need maintenance on other system components, such as batteries.

Wind Energy

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Modern wind turbines use the wind's lift forces to turn aerodynamic blades that turn a rotor which creates electricity. In the UK we have 40% of Europe's total wind energy. But it's still largely untapped and only 0.5% of our electricity Fig 6.2 requirements are currently generated by wind power. wind power is proportional to the cube of the wind's speed, so relatively minor increases in speed result in large changes in potential output. Individual turbines vary in size and power output from a few hundred watts to two or three megawatts (as a guide, a typical domestic system would be 2.5 - 6 kilowatts, depending on the

location

and

size

of

the

home).

Uses range from very small turbines supplying energy for battery charging systems (e.g. on boats or in homes), to turbines grouped on wind farms supplying electricity to the grid. Small scale wind and your home Wind speed increases with height so it's best to have the turbine high on a mast or tower. Generally speaking the ideal setting is a smooth-top hill with a flat, clear exposure, free from excessive turbulence and obstructions such as large trees, houses or other buildings. However, small-scale building-integrated wind turbines suitable for urban locations are currently being developed and will be available to install in homes and other buildings within the next few years. Planning issues such as visual impact, noise and conservation issues also have to be considered.

Stand-alone or grid-connected system Small-scale wind power is particularly suitable for remote off-grid locations where conventional methods of supply are expensive or impractical. Most small wind turbines generate direct current (DC) electricity. Off-grid systems require battery

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storage and an inverter to convert DC electricity to AC (alternating current - mains electricity). You also need a controller to divert power to another useful source (e.g. space and/or

water

heaters)

when

the

battery

is

fully

charged.

It's common to combine this system with a diesel generator for use during periods of low wind speeds. A combined wind and diesel system gives greater efficiency and flexibility than a diesel only system. It allows the generator to be used at optimum load for short periods of time to charge batteries when there is little wind, rather than by constant use at varying loads. Wind systems can also be installed where there is a grid connection. A special inverter and controller converts DC electricity to AC at a quality and standard acceptable to the grid. No battery storage is required. Any unused or excess electricity can be exported to the grid and sold to the local electricity supply company. Cost and maintenance Systems up to 1kW will cost around £3000 whereas larger systems in the region of 1.5kW to 6kW would cost between £4,000 - £18,000 installed. These costs are inclusive of the turbine, mast, inverters, battery storage (if required) and installation, however it's important to remember that costs always vary depending on

location

and

the

size

and

type

of

system.

Turbines can have a life of up to 20 years but require service checks every few years to ensure they work efficiently. For battery storage systems, typical battery life is around 6-10 years, depending on the type, so batteries may have to be replaced at some point in the system's life. Biomass, contraction for biological mass, the amount of living material provided by a given area of the earth's surface. The term is most familiar from discussions of biomass energy, that is, the fuel energy that can be derived directly or indirectly from biological sources. Biomass energy from wood, crop residues, and dung remains the primary source of energy in developing regions. In

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a few instances it is also a major source of power, as in Brazil, where sugarcane is converted to ethanol fuel, and in China's Sichuan province, where fuel gas is obtained from dung. Various research projects aim at further development of biomass energy, but economic competition with petroleum has mainly kept such efforts at an early developmental stage.

Solar Collector Fig 6.3 A solar collector is a device for extracting the energy of the sun directly into a more usable or storable form. The energy in sunlight is in the form

of

electromagnetic

radiation from the infrared (long)

to

the

ultraviolet

(short) wavelengths. The solar energy striking the earth's surface at any one time depends on weather conditions, as well as location and orientation of the surface, but overall, it averages about 1000 watts per square meter on a clear day with the surface directly perpendicular to the sun's rays.

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Fig 6.4 A solar thermal collector that stores heat energy is called a "batch" type system. Other types of solar thermal collectors do not store energy but instead use fluid circulation (usually water or an antifreeze solution) to transfer the heat for direct use or storage in an insulated reservoir. Water/glycol has a high thermal capacity and is convenient to handle. The direct radiation is captured using a dark colored surface which absorbs the radiation as heat and conducts it to the transfer fluid. Metal makes a good thermal conductor, especially copper and aluminum. In high performance collectors, a "selective surface" is used in which the collector surface is coated with a material having properties of high-absorption and low-emissive. The selective surface reduces heat-loss caused by infrared radiant emission from the collector to ambient. Another method of reducing radiant heat-loss employs a transparent window such as clear UV stabilized plastic or Low-emissivity glass plate. Again, Low-E materials are the most effective, particularly the type optimized for solar gain. Borosilicate glass or "Pyrex" (tm) has low-emissivity properties, which may be useful, particularly for solar cooking applications. As it heats up, thermal losses from the collector itself will reduce its efficiency, resulting in increased radiation, primarily infrared.

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This is countered in two ways. First, a glass plate is placed above the collector plate which will trap the radiated heat within the airspace below it. This exploits the so-called greenhouse effect, which is in this case a property of the glass: it readily transmits solar radiation in the visible and ultraviolet spectrum, but does not transmit the lower frequency infrared re-radiation very well. The glass plate also traps air in the space, thus reducing heat losses by convection. The collector housing is also insulated below and laterally to reduce its heat loss. The second way efficiency is improved is by cooling the absorber plate. This is done by ensuring that the coldest available heat transfer fluid is circulated through the absorber, and with a sufficient flow rate. The fluid carries away the absorbed heat, thus cooling the absorber. The warmed fluid leaving the collector is either directly stored, or else passes through a heat exchanger to warm another tank of water, or is used to heat a building directly. The temperature differential across an efficient solar collector is usually only 10 or 20°C. While a large differential may seem impressive, it is in fact an indication of a less efficient design. For solar heating of domestic hot water, two common system types are thermosyphon and pumped. In the thermosyphon system, a storage tank is placed above the collector. As the water in the collector is heated, it will rise and naturally start to circulate around the tank. This draws in colder water from the bottom of the tank. This system is self-regulating and requires no moving parts or external energy, so is very attractive. Its main drawback is the need for the tank to be placed at a level higher than the collector, which may prove to be physically difficult. A pumped system uses a pump to circulate the water, so the tank can be positioned independently of the collector location. This system requires external energy to run the pump (though this can be solar, since the water should only be circulated when there is incident sunlight). It also requires control electronics to measure the temperature gradient across the collector and modulate the pump accordingly.

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Systems using solar electric pumping and controls are known as Zero carbon solar while those using mains electricity are known as low carbon, since they typically have a 10-20% carbon claw back Solar collectors can be mounted on a roof but need to face the sun, so a northfacing roof in the southern hemisphere and a south-facing roof in the northern hemisphere is ideal. Collectors are usually also angled to suit the latitude of the location. Where sunshine is readily available, a 2 to 10 square meter array will provide all the hot water heating required for a typical family house. Such systems are a key feature of sustainable housing, since water and space heating is usually the largest single consumer of energy in households.

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Geothermal Heat Exchange Pump

A geothermal exchange heat pump, also known as a ground source heat pump, is a heat pump that uses the Earth as either a heat source, when operating in heating mode, or a heat sink when operating in cooling mode. All geothermal heat pumps are characterized by an external loop containing water or a water/antifreeze mixture (propylene glycol, denatured alcohol or methanol), and a much smaller internal loop containing a refrigerant. Both loops pass through the heat exchanger. Air source heat pumps use the same principle but extract the heat from the air, rather than the ground. As such their installation is much simpler and cheaper. Heat pumps are especially well matched to under floor heating systems, rather than wall mounted radiators, and so are ideal for use in open plan offices. Using large surfaces such as floors, as apposed to radiators, distributes the heat more uniformly and allows for a lower temperature heat transfer fluid. The Earth below the frost line remains at a relatively constant temperature year round, usually between 7-21 degrees Celsius (45-70 degrees Fahrenheit) depending on geographical location. Because this temperature remains constant.

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Geothermal heat pumps perform with far greater efficiency and in a far larger range of extreme temperatures than conventional air conditioners and furnaces. To understand how a heat pump can heat during the winter and cool during the summer, let us consider each mode:

Heating mode In the heating mode, the external fluid is pumped from the well at 8-16 degrees Celsius and passes through the heat exchange unit. Within the heat exchanger the internal fluid is allowed to expand and change state into a gas, which draws heat (heat of vaporization) from the external fluid, thereby cooling the external fluid. Meanwhile the internal gas is pumped to the compressor where it is pressurized causing it to condense into a liquid, which releases the heat and the heat exchanger warms the neighboring air of the house. At the same time, the cooled external fluid is pumped back into the closed loop running into the earth where it is warmed by the soil and recirculated.

Cooling mode The cooling cycle is very similar except a valve on the internal loop reverses the direction of flow. Now the compressed internal fluid coming from the compressor heats the external fluid, before passing through the evaporator where it vaporizes taking up heat from the air in the house. The heated external fluid is pumped into the ground where it is cooled and recirculated. Alternatively, the heated fluid may pass through a second heat exchanger where water from the house absorbs some of the excess heat. This means that in summer, the house air is cooled and the hot water is heated by the heat pump.

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Potential Advantage of ZEB •

it appears to isolate the buildings occupant(s) from energy price increases

•

buildings built using ZEB concepts tend to be more comfortable due to more uniform temperature (this can be demonstrated with comparative isotherm maps)

•

it is substantially less expensive to improve energy efficiency during initial design and construction than it is to do so through a retrofit

•

higher resale value

•

the value of a ZEB building relative to similar conventional building increases as energy costs increase

Potential Disadvantages of ZEB •

first costs can be expected to be higher in the near term

•

future significant declines in energy costs could strand capital invested in energy efficiency

•

new technology in the field of solar cells could strand capital invested in a solar electric generating system

•

challenge to recover higher first costs on resale of building

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CONCLUSION The ZEB goal is technically achievable for significant portions of the commercial sector. This suggests that a ZEB goal is feasible and this goal can be used to direct research and other activities. Efficiency measures are important for reaching the ZEB goal. The amount of energy that can be saved by efficiency improvements is comparable to the amount that can be generated by current rooftop PV panels.

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References 2000 ZEB meeting report "Self-Sufficient Solar House " Fraunhofer Institute's (ZEB), Freiburg, Germany • AEO. (2006). Annual Energy Outlook 2006. Washington, DC: EIA. Available from                  http://www.eia.doe.gov/oiaf/aeo • •

• • • • •

DTI pages on Microgeneration The DTIs Low Carbon Buildings Programme Micro power Council The Green Alliance's Microgeneration Manifesto "Our Energy Challenge, Securing Clean and Affordable Energy for the Long Term" (a document by the DTI).

• •

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CERTIFICATE

This is to certify that, the seminar work entitled

Zero Energy Building Has been submitted by Mr.Chetan Annaji Waghmare In satisfactory manner as a partial fulfillment of award of degree of Bachelor of Engineering (Mechanical Engineering) Sant Gadge Baba Amravati University, Amravati.

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GUIDE

Prof. A.M. Mahalle

H.O.D.

Prof.Mrs. S.R.Charde

Department Of Mechanical Engineering Government College of Engineering Amravati. 2006-07

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