Energy Science Fair Projects About Solar Hot Water Systems

Hot Water

A lot of the energy that a home uses is used to heat water for baths, cooking and cleaning. Can this water be heated using solar energy?

Objectives/Goals

The objective was to measure the efficiency of our family's photovoltaic (PV) and solar hot water (SHW) systems in order to determine which technology does a better job of turning the sun's energy into an alternate form. The cost effectiveness of each technology was examined.

Methods/Materials

For the solar hot water panels, the efficiency was found by measuring the temperature of the water flowing into and out of the panels, the flow rate, the solar irradiance, and the area of the panels. Data from the temperature sensors and a pyranometer was taken once per minute and logged by two computers. The efficiency of the photovoltaic panels was found using the output power of the photovoltaic inverter and the pyranometer. A third computer was used to log the output of the pyranometer once per minute. Data from the text files was put into Excel for calculations and plotting.

Results

Data was taken over a three day period from 1/31/09 to 2/2/09. All three days were clear and sunny. The data from each day was similar. In the morning, the solar irradiance (W/m2) rose gradually dropped and reached a maximum around noon. The solar irradiance fell off suddenly at 3:15 pm each day as shade from our neighbor#s tree fell across the meter. The efficiency of the solar hot water panels was determined to be about 20% for most of the day. The efficiency of the photovoltaic panels was 12%.

Conclusions/Discussion

It was found that a solar hot water panel is more efficient at turning the Sun#s energy into an alternate form than a photovoltaic system. The solar hot water system was also less expensive than the photovoltaic system by a factor of about two. Since the SHW system is about twice as efficient as the PV system at about half the cost, the SHW is about four times as cost effective as the PV system. 3rd party contributor

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