Solar Energy Physics 1303

Three forms of solar energy.  Passive Solar  Active Solar  Photovoltaic

Passive Solar Energy  Sensible architectural design  Use sun in the winter  Avoid in the summer.  Cold climates- large glazing which may be insulated at night and opened during the day.  Hot climates - blocking the sun and providing good ventilation.

Passive Design Arizona Cliff Dwelling is an example of traditional low- tech solution to space heating and cooling needs.

Passive Design This is a modern New Mexico version. There is movable isolation to put in place at night.

Passive Design Another interesting design. The wall is down and the passive collector is collecting solar energy

Passive Design In this mode, the wall is up and the building is storing solar energy or blocking summer heat gain.

An innovative passive design Roof Pond House in Atascadero, California

Active Solar Energy  Use pumps and solar collectors to provide energy.  Two types of solar collectors: –flat plate –concentrating

Flat Plate Collector  Made of a black absorbing plate with water running through it or air blowing past it.  Usually a flat plate collector has a glazing to stop heat from escaping.  Efficiency 50% or better.

Flat Plate Collector Hot Water Heater Low cost heater in the roof of this modest Miami house

Flat Plate Collector Hot Water Heater Low cost heater in the roof of this modest San Antonio house

Flat Plate Collector Hot Water Heater  Solar water heater system has four components:  Collector  Tank  Pump  Controller

Flat Plate Collector Flat Plate Collector components:  Plate with tubing  Insulation  Glazing

Concentrating Collector  A concentrating collector includes some kind of lens or mirror.  Tracks the sun.  High temperature.  Efficiency near 50%.

Concentrating Collector Components:  Optics  Glazing  Absorber  Insulation  Tracking

Concentrating Collector This one uses a mirror and has no glazing

Concentrating Collector Used to be on the roof of the Bell center.

Concentrating Collector This is the solar concentrating collector on the CPS Headquarters building on San Pedro. It runs the air- conditioning system

Flat Plat Collector Problem Let’s work a problem

Solar Hot Water Heater

Flat Plate Collector Problem A flat plate solar collector is used as a solar hot water heater. The collector area equals 20 square meters. The collector is located in a location with annual average daily solar insolation equal to 5.0 kWh/square meter/day.

1. Calculate the amount of solar energy incident on this collector each day. Solar Energy = = 5.0 kWh / sq m / day 20 sq m = 100 kWh / day

2.Assuming that the efficiency of the solar collector and the rest of the system equals 50%, calculate the average daily energy produced (as hot water) by this system. Express your answer in kWh/day. Average Produced Energy/day = = 100 kWh / day 0.50 = 50 kWh / day

3. Calculate the amount of energy produced by this system each year. Express your answer in kWh. Annual Energy Production = = 50 kWh/day 365 day/year = 18,000 kWh / year

4. Assuming that the solar energy replaces the heating of hot water by electric energy and that electric energy cost 10¢/kWh, calculate the yearly savings in electricity costs as a result of using the solar hot water system. Express your answer in $/year. Money Saved = = 18,000 kWh $0.10/kWh = $1,800 / year

5. Suppose this solar hot water system were to cost $5,400 (installed). Calculate the payback period for this system Payback = Cost / Savings = $5,400 / $1,800 /year = 3 years

Photovoltaics  Photovoltaic systems convert solar energy directly into electricity. They have efficiencies near 10%.

Photovoltaics PV-powered airplane. Is this really a good idea?

Photovoltaics PV arrays are widely used for low power loads.

Photovoltacis A PV array is made up of several panels and a panel is made up of several cells.

Photovoltaics A complete system has an array, a battery, an inverter and a load. The system can supply either DC or AC loads.

Photovoltaics The inverter converts the DC voltage from the PV array into an AC signal to power AC loads or to connect to the grid.

Photovoltaics  Laurel Kaesler and Frank Ehman designed and built the PV Project in the Physics Department

Photovoltaics  The PV project has 4 components:  Array  Controller  Battery  Load

Photovoltaic Controller

Photovoltaics  The load is a pair of fluorescent lights that I use in a small 3 rd floor lab in MMS

Photovoltaic This is the solar array on the CPS Headquarters building on San Pedro.

Photovoltaic  The output of the array is inverted into an AC voltage and fed back to the grid.

Photovoltaics A high-tech solution is to use PV to capture sunlight as electricity and use the electricity to produce microwaves that are beamed back to earth.

PV Problem Let’s work a PV problem.

Photovoltaic Power System

PV Problem A photovoltaic power system has a collector area equals 100 square meters. The collector is located in a location with annual average daily solar irradiance (insolation) equal to 5.0 kWh/square meter/day.

1. Calculate the amount of solar energy incident on this collector each day. Solar Energy = = 5.0 kWh / sq m / day 100 sq m = 500 kWh / day

2.Assuming that the efficiency of the PV array and the rest of the system equals 10%, calculate the average daily energy produced (as electricity) by this system. Express your answer in kWh/day. Average Produced Energy/day = = 500 kWh / day 0.10 = 50 kWh / day

3. Calculate the amount of energy produced by this PV system each year. Express your answer in kWh. Annual Energy Production = = 50 kWh/day 365 day/year = 18,000 kWh / year

4. Assuming that the cost of electric energy equals 10¢/kWh, calculate the value of the electricity produced by this system annually. Value of energy or Savings = = 18,000 kWh $0.10/kWh = $1,800 / year

5. Suppose this PV system were to cost $27,000 (installed). Calculate the payback period for this system. Payback = Cost / Savings = $27,000 / $1,800 /year = 15 years

Solar Energy Do you think solar energy will able to replace a significant fraction of the energy needs of our society?