KEEPING IT WARM:
EXPLORING THE HEATING OPTIONS OF WINTER PRODUCTIVE GREENHOUSES
Madeline Hansen
Environmental Studies CSB|SJU
Advisors: Dr. Jean Lavigne and Dr. Derek Larson
Abstract
Heating winter greenhouses is costly. Environmental sustainability is often marginalized when only the market price of heating systems is considered. Heating systems are the largest factor
in determining the environmental impact of winter greenhouses, as well as the greatest cost for running a greenhouse. This paper examines which heating system (natural gas, propane,
waste-heat water, biodigester, biomasss, geothermal, and solar power) is the most economical and environmentally responsible. I conducted a literature review examining the different
heating systems and analyzed their average Btu consumption for large and small greenhouse when heated to 50°F during a typical winter season (October-March). From this examination I
have concluded that ground source heat pumps provide the best solution to heating a winter greenhouse when taking into account both the environmental and economic costs.
Methods
http://www.poly-tex.com/
Commercial Greenhouse (4,320 ft2) Heating Data
http://www.farmtek.com/farm/supplies/home
Two greenhouses were chosen to act as models
to standardize the size and construction
materials. An equation was then used to determine
the minimum required heat output for each structure.
Once these models were selected a literature review
was used to gather data regarding each potential
heating system. This data was then complied and
analyzed to determine which heating system had both
the lowest environmental and economic costs.
2
Residential Greenhouse (288ft ) Heating Data
Heating
Systems
Natural Gas
Propane
Fuel Price
per Unit
$10.51
$43.65
Biomass (wood pel$15.15
let)
Solar Thermal
$0.00
Solar Passive Volta$0.00
ic
Geothermal
Passive Solar +
Back-up
$0.00
< $10.51
Fuel Cost per
Million Btu
$10.52
$43.69
Capital
Cost
$329.00
$329.00
Maintenance
Complexity
Cost and Ease
Minimal,
Simple
Minimal,
Simple
$19.43
$2,749.00
$0.00
$2,590.10- Minimal,
3,453.47
Simple
$0.00
$13,301.93
$0.00
$2,249
< $10.512
Price of
backup
heater
Moderate
Minimal,
Simple
Minimal,
Simple
Simple
Simple
System
99.90%
99.90%
Expected lifetime of system
Efficiency of
System
Expected
lifetime of
system
Natural Gas
$10.51
$13.14
$1,795
Minimal, Simple
Simple
80%
10 years
Propane
$43.65
$54.55
$1,795
Minimal, Simple
Simple
80%
10 years
Waste-heat water
$0.00
$0.00
$220,000
$2,000, Moderate
Difficult
20 years
Biomass
$15.15
$20.20
$10,015$22,033 ha-1
$5,034.23$10,068.47 yr,
Moderate
Moderate
75%
20 years
Biodigester
$0.00
$0.00
$7,728/kW
$.015/kWh ModerModerate
ate
50%
20 years
Solar Thermal
$0.00
$0.00
$38,88051,840
Minimal, Simple
Simple
20%
10 years
Geothermal
$0.00
$0.00
$19,550
Minimal, Simple
Moderate
Coefficient of
25-50 years
Performance: 3.3
10 years
10 years
Moderate
78.00%
Simple
20% of available
10 years
solar energy
Simple
14.59%
10 years
Moderate
COP of 3.3
25-50 years
Simple
20% of available Lifetime of strucsolar energy
ture
Minimal,
Simple
Efficiency of
Heating Systems
Fuel Price
Fuel Cost per
Maintenance Cost
per Million
Capital Cost
Complexity
Million Btu
and Ease
Btu
10 years
Conclusion
From this analysis, I concluded that a passive solar system with a back-up heater is
the most economical choice as well as the most environmentally sensitive choice
for a residential greenhouse. A geothermal or ground source heat pump is the
most economical and environmentally sensitive choice for a commercial
greenhouse. Neither of these systems have the environmental costs that are
associated with fossil fuels. Further research should examine the productivity of
each greenhouse model while comparing heating systems