Solar Heating and Solar Heat Recovery for Greenhouses. John Archibald American Solar, Inc.

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1 Solar Heating and Solar Heat Recovery for Greenhouses Energy Savings In Greenhouses and Nurseries Conference August 2, 2006 John Archibald American Solar, Inc.

2 Solar Air Heating and Solar Heat Recovery for Greenhouses Rising Energy Costs Alternatives to High Energy Costs Efficiency Upgrades Solar Heating Solar Heat Recovery Solar Heating Approaches New Solar Heating Technologies New Solar Heat Storage Technologies Solar Heat Recovery with Thermal Storage Controls Cost, Savings and Other Benefits

3 Rising Energy Costs US commercial Propane price/gal $0.77, $1.05, $1.47, ~$2.00 Maryland residential Propane price ~$2.50/gal $27.50/million BTU to $2/gal Third highest in US after New Jersey and Rhode Island MD residential Heating Oil price/gal $0.94, $1.34, $2.13, ~$2.50 $22.50/million BTU to $2.50/gal MD residential Natural Gas price/million BTU $2.85, $8.42, $12.34, ~$16.50 $20.60/million BTU to $16.50/million btu

4 Rising Energy Costs Heating Costs are one of the largest variable costs in greenhouse operations Volatile energy prices make budgeting difficult Energy efficiency measures can help somewhat Timing planting can help somewhat Cold hardy plants can reduce energy use somewhat But customers demands drive timing and plant type Heating can be the difference between profit and loss

5 Low Temperature Heating Dominates Energy Use Greenhouses Required greenhouse temperature less than 80 degrees F Daytime solar heat covers most daytime heating needs Daytime solar heat buildup often exceeds heating needs, Ridge temperatures can reach 100+ deg F Often require ventilation which wastes solar heat gains

6 Greenhouse heating for night time and ventilation Up to 80% of annual heating need is at night Nighttime thermal controls ( blankets, etc.) cut heating needs. Ventilation adds to heating needs Ventilation required for Humidity control, O 2 for combustion air supply and air quality CO 2 control Inflation fan air supply

7 Solar Heating Alternatives Active Heating Systems - pump air or water Low temperature pool heating < 110 deg. F Mid temperature water heating panels deg.f Air heating 70 up to 240 deg.f High temperature (water, steam, hot oil) up to 750 deg.f Cost per sq ft Low temperature pool heating, $9-12 Mid temperature water heating panels, $35 - $50 Air heating, $7-15 High temperature, $

8 Solar Air Heating Systems Solar Air Heating Systems low cost $7-15/sq ft collects 30+% of sunlight low, mid, and high temperature systems available displaces space heating, water heating, drying and industrial heating energy use (gas, electric, fuel oil, propane, etc.) 5-10 year old technology --- updates 100 year old systems 3-6 year payback (<1 year payback available with financing) Appearance ground mounted polymer panels offer best economics metal roof and flat or corrugated siding systems hidden flat roof and roof screen systems

9 Heater Boards, Polymer Low cost polymer collector Heats air Tested at NC State Installed at residential and government facilities High temperatures, up to 70 degrees F above ambient Recommended operation at 40 degrees above ambient for higher efficiency Optional glazing for efficiency boost Portable to free up outdoor space for setting crop in warmer weather Air Heating Collectors

10 Under floor heat energy storage using air ducts Advantages Higher night time / morning air temperature, ~5ºF higher at 8AM Higher root zone / floor temperature soil surface temperature ~5ºF higher at 8AM and as much as ~18 ºF at 8AM, 10 below the surface ~ 8ºF degrees warmer air and soil after several snowy/cloudy days Reduced humidity with condensation in underground ducts Reduces ventilation in early spring and late fall for humidity control Reduced peak afternoon temperatures can reduce ventilation

11 Underground heat energy storage using air ducts Glazed south wall greenhouse (left) With insulated north wall (right), Size 17 wide, 7.5 high showing arrangement of ducts placed 1.5 below floor and emerging above floor at west end of greenhouse

12 Adjacent earth energy storage using air ducts for space heating Advantages Does not disturb existing floor or water based floor heaters Dirt cheap storage media, Dirt, organic insulation (straw, etc.), used plastic film covers Higher night time / morning air temperature, Reduced humidity with condensation in underground ducts Reduces ventilation in early spring and late fall for humidity control

13 Site Built, Polymer Air Heating Collectors Low cost polymer film collector system Heats air Uses available outdoor space in cold months Can use waste materials, old polymer greenhouse covers Temperatures up to 50 degrees F above ambient Earthen mounds for heat storage Can be disassembled to provide space for plants moved out of greenhouse in warmer months

14 What makes a good solar application? Don t try to make solar meet 100% of the peak energy needs for large systems Use solar to cut annual costs of large energy systems Displace electric, propane, oil heat with solar heat Avoid high temperatures to feed conventional heating systems E.G., Boiler return water preheat Minimize thermal storage costs Minimize thermal storage hardware costs Minimize air-water-air heat exchange Year round load Make the system repay investment every day the sun shines Pre-charge thermal storage for more seasonal gains

15 Low installed cost under $15/sq ft High solar efficiency What makes a good solar application? 10 to 30 units of solar energy gathered for every unit of energy used to run fans or pumps greater than 20% of available solar energy converted to heat Building integrated makes building walls or roof do double duty (weather envelope or facade and energy production) for no extra cost Buy the energy not the system, if capital funds are not available but operating funds for energy bills are

16 Where should solar air heating systems be deployed? Low temperature air - less than 110 deg.f Ventilation preheating in cold climates High volume low temperature drying applications Mid temperature air deg.f Boiler air pre-heating all climates Ventilation air heating and preheating Heat pump pre-heating Hot water heating with air to water heat exchanger Air radiant floor and under floor ventilation

17 Pentagon Loading Dock Solar Heating Loading Dock operates at ambient temperature Gas overhead heaters for freeze protection, too hot close to work from back of truck bed Morning through early afternoon operation requires thermal storage Designed in hybrid heat recovery from excess industrial process heat

18 Pentagon Loading Dock Solar Thermal Storage Schematic

19 Thermal Storage and Controls -500 gallon water thermal storage, -2 tanks -adapted for hybrid heat recovery from industrial process heat -controls for solar roof fans -Simple on-off controls whenever solar heat can be collected

20 Loading Dock Solar Heating Performance Test begins Solar heating (3) Night, fan off, pump on (1) (2) (4) Test Ends (1) local room heating sensors (2) fan on, solar heating (3) pump off, Outside air >85F manual reset for pump start (4) solar heating

21 What is solar energy worth What s this raw sunlight worth? It s worth the amount of heating dollars it saves in traditional heating fuels, (e.g., gas or electricity) Solar heat, Practical case, 30% collection efficiency, year round At $20/million BTU ($2/therm) cost of natural gas, solar ~ $0.002/sq ft/hr, $0.02/ sq ft/day, $4-8/sq ft/year At $0.08/kwhr cost of electricity, $4-8/sq ft/year

22 The Cost of Delivered Heat From Different Energy Sources Compared to traditional energy sources Current $ per Million BTU American Solar air heat $ $9.00 Electricity $27.00 ($14 heat pump) Propane $27.50 Fuel oil $22.50 Natural gas $20.60 Other Solar Technologies Comparable solar heat $15.00 Solar electric (photovoltaics) $ $45.00 Prices of traditional fuels projected to rise.6 to 1.8% per year through 2025 (US EIA)

23 Commercial Solar Economics Commercial Solar Heating Systems provide 4 economic benefits energy cost savings 1st year, 30% tax credit accelerated depreciation 5 year MACRS for remaining 85 % of cost 20%, 32%, 19.2%, 11.52%, 11.52%, 5.76% per year ~71% depreciated in 3 years stable energy prices natural gas prices projected to rise 1.8%/yr. for 20 years

24 Commercial Solar Economics Financing a heating system can be cash positive from day one. System with 5 year payback will return: 20% energy savings each year 30% 1st year tax credit est. 17% depreciation 1st year tax savings (@ 34% tax rate) Total 1st year savings 56% 5 year loan at 6% first year payment = 23.7% First year savings 32.3% of purchase price Buy the heat - not the hardware if capital funds are not available but operating funds for energy bills are

25 Solar energy works better and does more than ever before! New building integrated technologies New solar and storage technologies and techniques New solar applications Ventilation air, water heating, heat pump preheat, boiler air Lower installed costs Higher energy delivery Attractive economics Lowest cost source of heat