heater to heat the green house and the water tanks. Also we can use this system for other needs of
greenhouse like lighting pumps and every other equipment that operates with electricity. The solar
water heaters are explained in detail below.
Considering our greenhouse location and size we assume a system to be between 4-7 kW. We have the
area defined as 33 L x 22 W. Assuming also that we will need to use 100 G of water every day at a temp
of 120 F and the green house will be 10 ft. high. The start-up costs for each heater are show in Appendix
N.
Taking in consideration the efficiency and the demand for free energy over the years we put in place
another option. Solar energy is cost effective during the years but it is expensive in the startup as the
table above shows. Another technology that is related to solar but less expensive is Solar Water Heaters
or SWH. So instead of using a system that converts the solar energy to electrical energy we are going to
use solar water heaters. This technology converts the solar energy to thermal one.
The SWH will be used as primary heat source and the electrical heater will used as a secondary .They will
basically complement each other. The table below shows the components and costs for setting up a new
system.
The figure 13 shows the differences in cost between various heating solutions and also the Return-of-
Investment (ROI) in 10 years.
Figure 21. Costs and ROI over 10 years of different Systems
The water heating system will be one most costly part for our greenhouse especially in long term. Using
a solar water heater combined with electrical heater would be an attractive option. The SWH will be
used as primary heat source and the electrical heater will used as a secondary .They will basically
complement each other. The start-up cost is basically low compared with the other systems and solar
offers long term savings. Also something to keep in mind is the greenhouse itself will provide heating
due to the greenhouse effect, similar to how a solar hot water heater would work, but for internal
systems without natural light, a solar hot water heater + electric heater backup would be attractive.
Electrical
Natural GasSolar PVFirewood
SWH$0.00$2,000.00$4,000.00$6,000.00$8,000.00$10,000.00$12,000.00$14,000.00Electrical Natural Gas Solar PV Firewood SWHAverage ROI