Solar Heating Presentation

SOLAR HEATING Domestic Hot Water, Space Heat, Heat Storage Michael Woods Comm Ave LLC 1

Michael Woods Engineer/Consultant

Comm Ave LLC: Green Energy Upgrades Energy Audits, System Design, Install Solar Geothermal Heat Pump Dual Fuel Residential Systems

2

4 years designing solar heat/hot water systems Conducted solar study into seasonal storage Installed 30-Tube Thermomax Evacuated Tube ‘test rig’ as Domestic Hot Water 3

o o o o o o

Solar Radiation Basics Domestic Hot Water Heating House Heating Solar Site Evaluation Sizing and Cost Questions

4

1972 National Science Foundation Testimony: “Solar energy is an essentially inexhaustible source potentially capable of meeting a significant portion of the nation’s future energy needs with a minimum of adverse environmental consequences…the most promising of unconventional 1

5

Solar radiation comes from the Sun. It can be direct, diffuse or reflected. Radiation is measured by wavelength. Most Solar: 0.1 – 3.0 x 10-6 m (micrometers, μm) Thermal Radiation (Heat) Range: 0.1 -100 μm

Solar radiation is used for heating applications by absorbing the solar radiation and transforming it to thermal

6

X-Ray

Ultra-Violet

Composite Infrared

Visible

Radio 7

Insolation: Incoming Solar Radiation Measurement of the amount of energy incident on an area for a given time. Insolation includes direct, diffuse and reflected radiation. Units: Energy / Area x Time BTU/ft2 · hr (English Units) I’ll try to stick to these. kWhr/m2 · day or W/m2 (Metric, 1 Watt = 1 J/s) 8

Tilt angle presently 23.5° Groton’s Latitude is 42.6°N On the Summer Solstice, the sun is 70.9° from the horizon. On the Winter Solstice, the sun is 23.9° from the horizon. Tilt > Distance Sun is closer to Earth in Winter Sun is more distant in

Above: Earth’s Position at Summer Solstice

9

Incidence Angle: The angle between the sun and the Normal of the surface it strikes Azimuth Angle: The angle between due south and the Normal of the surface Normal: Perpendicular to the surface

10

4 Examples to illustrate effect of tilt & incidence angle All examples take place at 40°N Latitude (Trenton NJ) Example #1: Solar noon on the Summer Solstice 45° (Normal) Roof facing Due South 90% of max 28° = incidence angle. Percent of max. insolation: 90% Roof 45° Compare this to….. Facing South

11

45° Roof Gained 90% of Maximum Insolation Example #2: Solar noon on Summer Solstice 0° (Normal) Wall facing Due South 73° incidence angle. Wall 0° South Percent of Max insolation: 32% Facing 32% of max 12

Example #3: Solar noon Winter Solstice 0° (Normal) Wall facing Due South 26° incidence angle (sun is lower in the sky) Percent of Max insolation: 82%

82% of max

Wall 0° Facing Due South 13

Wall Facing South Gained 82% of Maximum Insolation Example #4: Solar noon Winter Solstice 0° Wall facing South West Same 26° angle (up/down). 45° East of Due South (left/right). Percent of Max insolation: 59% 59% of max

Wall 0° South West Facing (Azimuth = 45° from S) 14

The Sun: Powerful, Clean, Inexhaustible Spectrum of wavelengths, Thermal vs. Solar Earth Tilt Effects are seasonal Surface Tilt Effects are local Angle between sun and normal to the surface changes the potential insolation 15

Terminology Collector Type Collection Methods Other System Components

16

Terminology Collector: Surface that absorbs solar insolation and transfers it to a working fluid Working fluid: Water or antifreeze solution heated by collector and transfers heat to a storage tank Circulator: Pump that moves working fluid through an active gain system from collector to storage tank Heat exchanger: section of system 17

Collector Type Flat Plate Collector Evacuated Tube Collector

18

Collector Type: Flat Plate Collector Most common type of collector Temperature Range: 90°-160°F Absorber surface is Flat Enclosure Insulated Glazing layer/layers Working fluid moves heat Heat transfer via conduction and forced convection 19

Flat Plate Collector Pros: Low up front costs (used collectors are available) Very DIY friendly Good value for Low Temp. applications (pool, pre-heat tank)

Cons: Difficult to insulate well Low collection efficiency Heavy (roof mounting) Glazing issues Incidence angle losses are high 20

Evacuated Tube Collector New Collector type Temp. Range 90°-250°F Absorber surface inside 2 glass tubes Vacuum between tubes creates insulating condition. Working fluid in heat pipe boils, condenses at end where transfer occurs. Solar radiation always normal to Tube Surface

21

Evacuated Tube Collector Pros: Very efficient collectors Lightweight High Temp. applications (dual-coil DHW tanks) One broken tube doesn’t spoil the bunch

Cons: Expensive Temperature range can be dangerous/damaging Antifreeze breakdown is quicker

22

System Type Active Gain Closed Loop (CL) Active Gain CL Drainback Natural Circulation Thermosiphon

23

Active Gain/Closed Loop

24

Closed Loop System Pros: Can tie into existing DHW system (pre-heat tank) Most common DHW system Minimal controls requirement

Cons: Antifreeze or Line heaters required in cold climates Line break could quickly damage system Moving parts = maintenance 25

Active Gain CL Drainback

26

Drainback Systems Pros: No need for antifreeze Less maintenance than non-draining CL systems (not under pressure) Can tie into existing DHW system (pre-heat tank)

Cons: More controls required (drainback valve) Less common in industry Moving parts = maintenance 27

Natural Circulating Thermosiphon System

28

Thermosiphon Systems Pros: No moving parts Lowest up front costs

Cons: Collector must be below storage tank Heat transfer depends on minimizing friction in pipes When collector temp < storage tank temp flow reverses Antifreeze required for year-round use in cold 29 climates.

Other system components Controller Thermocouples Pumps Storage Tank (Superstore, Dual-Coil, Outdoor Shower) Piping (Copper, PEX) Expansion tank Reservoir Overheat/overpressure valve Air bleed 30

Panel Types: Flat Plate vs. Evacuated Tube Active Gain, Natural Circulation, Drainback Maintenance, Antifreeze Tie-in to DHW

31

Direct Gain Indirect Gain Active systems Passive systems Storage systems

Bob G

agnon

’s Eva cuated

Tube M ega-A

rray

32

• Open Floor Plan and ceiling fans to reduce heat stratificaiton • North Side of house burmed into hill to reduce heat loss • North walls painted brown/green/blue to absorb

33

34

35

Two Views: Trombe Wall 36

37

38

Fan Coil System, Similar to Solar

39

Single Coil DHW Tank 2.Supplies pre-heated water for on-demand propane heater 3.Heated water then goes to either DHW or Heat exchanger to heat Radiant Floor Loop 40

Best solar designs happen before house is built Adapting solar is limited without storage Indirect systems work best for existing homes Radiant heating systems deliver best value 41

How to determine your potential for solar? Before going on……some questions to ponder: What are your goals for using solar? What is the long term plan for your home? What is the energy use in your home? How is the expected energy use going to change in the short-term/long-term? 42 What are the aesthetic requirements at

Solar Potential: Viable solar options depend on having enough available insolation and enough demand for that heat. Tools to measure available insolation: Compass: Find South, minimize shading. Pyranometer: Measures all insolation Direct/Diffuse Sun Path diagrams: Manual calculation, fairly tricky Solar Pathfinder (Available for free!)

43

Solar Pathfinder Software Screen Allows for multiple inputs User input latitude, tilt and azimuth of each location Example: Upper portion of Leo’s 44

Pathfinder properly aligned and level Reflection of surrounding obstructions (trees and buildings) can be seen on dome. Load picture into software for shade trace 45

46

47

Final Report Output options Daily available Insolation % of Ideal Insolation Shading losses Alignment losses KWH generation for PV $ generated by PV array All output given by

48

Insolation is only one piece of the puzzle Other design issues: Heating demand and insolation are naturally out of sync. Tilt collector to gain more insolation in winter months

Most shading in morning or afternoon Adjust azimuth and tilt to gain more when insolation comes thru Account for deciduous shading vs. coniferous shading Can trees be removed/trimmed?

What if the best location for solar is on your

49

Non-design considerations: Capital/Payback Investment in Solar must outweigh other investment options Utility cost reduction is primary measure of payback Reduction in system maintenance & replacement cost

Rebates Current federal rebates are an UNCAPPED 30% on ALL work associated with solar energy installation (audits, trades, tree work, parts, architects) Massachusetts rebates are up to 15% cap at $1,000

50

Additional planning into overall house systems should be considered before “going solar”. Strong evidence supporting GG reduction of over 60% for US homes to reach sustainable carbon emissions level. More than just solar water heating. Some of the best options (heat pumps, ondemand heat/hot water) will affect design of solar application. Energy use data and energy audits are a key step to proper planning and research. http://blip.tv Search: “Groton Local” Home 51 Energy Audits for more information

Determine Insolation (free!) Audit your energy use Set Solar Goals: DHW, Heat, GG Reduction Determine Capital/Payback/Rebates etc. Plan and Execute

52

Rules of Thumb Solar Hot Water: Avg. per capita daily hot water use: 18 gallons Energy requirement in N.E.: 12,300 BTU/day Design collector to cover 100% DHW in June “Good” site in June will receive daily insolation ~ 1,700 BTU/ft 2 Flat plate efficiency 35-70%, 15 ft 2/person Evac. Tube efficiency 45-85%, 9 ft 2/person53

The Challenge: Coldest day this year: Avg. T = 2.6°F, 1/16/09 On such a day: Avg. heat load per house: 1 million BTU/day Avg. insolation in January: 536 BTU/sq. ft./day Area of 100% efficient collector to 54