Lab: PV, solar thermal efficiency

Lab: PV, solar thermal efficiency

• Start with solar radiation: http://10.14.62.8
• W/m^2 is the solar energy falling on every m^2 here now

Photovoltaic (PV) panel

1. Select a Photovoltaic (PV) panel, note the red (+) and black (-) wires
2. Measure the area of the panel with a meter stick
3. Measure the voltage of the panel with no load
4. Connect a hot water heater to the panel, measure voltage under load.
5. Connect a current meter (see diagram below) between the + wire and the hot water heater.
6. Measure the current under load
7. Disconnect everything and measure the resistance of the hot water heater

Calculations:

1. calculate ideal energy falling on the panel, using solar radiation and panel area
2. calculate power delivered by the panel, using Volts and Amps
3. calculate power delivered by the panel, using Amps and Ohms
4. compare the power delivered by the power available
5. calculate efficiency: power out/power in
6. explain the difference

Solar Thermal (ST) panel

1. measure the area of the solar thermal (hot water) panel
2. turn on the cold water supply so that the water trickles out
3. using a 1 liter container, measure the time it takes to fill the container
4. measure the cold and hot temperatures for the panel

Calculations:

1. calculate the ideal energy falling on the panel, using solar radiation and panel area
2. calculate the ∆t between cool and hot water
3. calculate the calories delivered every second, using Q = mc∆t/time
4. convert calories/second to Watts (j/sec) by multiplying by 4.18
5. compare ideal power with measured power
6. calculate efficiency: power out/power in

Questions:

1. Which system is better at harvesting energy?
2. Which system has a more limited impact on your green home energy cost?
3. Which system can store energy for a longer time?
4. Why would some cities ban natural gas for water heating and cooking?
5. Suppose the roof on your green home is 20m long an 10 m wide. How much solar radiation is available to you?
6. Which system (PV or ST) would you install first and why?
7. Using the data from your hot water heater lab (the 4.5 kW water heater) how big would the panel need to be at your green home to cover this energy use, given a solar radiation of 1000W/m^2?

Using meter to measure current (Amperes):

1. Make sure wires are connected with red cable (+) to positive side and A on the meter, black cable (-) to the minus side (COM) in the middle of the flow
2. WARNING: do not connect meter in this configuration to measure anything other than current
3. Make sure to return red cable to the V outlet when done.