Solar Energy Basics Thermal and PV

Solar Energy – A Bright Idea! “I’d put my money on the sun and solar energy. What a source of power! I hope we don’t have to wait ‘til oil and coal run out before we tackle that.” - Thomas Edison

People have been harnessing solar energy for a long time! Solar collector for heating water A home in California in 1906

Sun Angles

Solar Photovoltaic (PV) Two Main Categories: Solar Thermal Solar Photovoltaic (PV) Water heating and cooking Electricity production

Solar Thermal Energy Cooking Water Heating

Solar Water Heating

Solar Water Heating Solar water heating is the most efficient and economical use of solar energy Residential systems start at $2500 and typically cost $3500-$4500 installed Savings of $30-$75 per month, lasting 20 years Tax credits and state rebates available

How Does it Work?

How Does it Work? Systems can be passive or active Passive systems only found in warmer climates, as they are prone to freezing Active: Roof-top collectors heat glycol which then passes through a heat exchanger in the storage tank to heat water Electric pump can be run on solar PV

Solar Hot Water Classroom Experiments Design your own SHW collector Variables: Color of collector Tubing length, pattern, material Light intensity Insulation Use of reflective materials Rate of water pumping Etc…

Solar Cooking

Benefits of Solar Cooking Consumes no fuels/wood No loss of trees & habitat Trees sequester carbon Generates no air pollution Generates no greenhouse gases Produces no smoke Cooking smoke kills over 1.6 million people each year, mostly women & children, according to a recent report Eliminates fire dangers

More Benefits of Solar Cooking Eliminates work No daily search for firewood 2 Billion people rely on wood for cooking fuel! No risks to women and children Frees time for other activities No need to stir food Helps to liberate women

More Benefits of Solar Cooking Cooks foods slowly and thoroughly Preserves nutrients Foods will not burn Pots are easy to clean; less clean water is needed Use for canning vegetables Use for dried fruit Kill insects in dry grains

Solar Cooking How Long Does it Take? Vegetables: 1.5 hrs Rice/wheat: 1.5-2 hrs Beans: 2-3 hrs Meats: 1-3 hrs Bread: 1-1.5 hrs

Fun Student Projects!

Solar Electric (Photovoltaic)

Solar Electric Systems Photovoltaic (PV) systems convert light energy directly into electricity. Commonly known as “solar cells.” The simplest systems power the small calculators we use every day. More complicated systems will provide a large portion of the electricity in the near future. PV represents one of the most promising means of maintaining our energy intensive standard of living while not contributing to global warming and pollution. Photovoltaic (PV) systems convert light energy directly into electricity. They are commonly known as “solar cells.” The simplest systems power the small calculators we use every day. More complicated systems will provide a large portion of the electricity in the near future. PV represents one of the most promising means of maintaining our energy intensive (with appropriate and technically viable efficiency gains) standard of living while not contributing to global warming and pollution. Solar Photovoltaics is the future of energy!

How Does it Work? Sunlight is composed of photons, or bundles of radiant energy. When photons strike a PV cell, they may be reflected or absorbed (transmitted through the cell). Only the absorbed photons generate electricity. When the photons are absorbed, the energy of the photons is transferred to electrons in the atoms of the solar cell.

How Does it Work? Solar cells are usually made of two thin pieces of silicon, the substance that makes up sand and the second most common substance on earth. One piece of silicon has a small amount of boron added to it, which gives it a tendency to attract electrons. It is called the p-layer because of its positive tendency. The other piece of silicon has a small amount of phosphorous added to it, giving it an excess of free electrons. This is called the n-layer because it has a tendency to give up negatively charged electrons.

How Does it Work?

Helpful PV Animations http://www1.eere.energy.gov/solar/animations.html http://www.managenergy.net/kidscorner/animations/solar_an.html

Best Place For Solar Panels? South Facing roof, adequate space No shading (time of year, future tree growth) Roof structure, condition

Large Scale PV Power Plants Prescott Airport Location: AZ Operator: Arizona Public Service Configuration: 1,450 kWp SGS Solar Location: AZ Operator: Tucson Electric Power Co Configuration: 3,200 kWp We have looked at various sources of distributed PV so far. On the other hand, utility companies are becoming more and more interested in centralized PV. These are two examples of PV in large centralized arrays. The right as 1,450 kWp system and the left has a 3,200 kWp system. To put this into perspective a large house might use 4-5kW. http://www.industcards.com/solar-usa.htm

Centralized Wind-Solar Hybrid System In hybrid energy systems more than a single source of energy supplies the electricity. Wind and Solar compliment one another This is an example of a centralized wind-solar hybrid system. Wind and Solar compliment one another. If it is cloudy and windy, the wind mills make up for the drop in solar energy. If it is not windy on a clear day, the solar panels can make up of the lack of wind energy. In hybrid energy systems more than a single source of energy supplies the electricity to the load. Sources: http://www.lged-rein.org/solar/stmartins/sre_stmartins4.jpg http://www.lged-rein.org/solar/solar_sre_stmartins.htm

Solar Concentrators These 20-kW Solar Systems dishes dwarf visitors in Alice Springs, Australia. The concentrators use an array of mirrors to focus sunlight onto high-efficiency solar cells. Four supports hold the cells in front of the mirrors The supports also supply cooling water and electrical connections Using solar concentrators can make economic sense when you are talking about centralized systems because mirrors cost less than PV. Each dish is a 20-kW Solar System in Alice Springs, Australia. The concentrators use an array of mirrors to track and focus sunlight onto high-efficiency cells. Four supports hold the cells in front of the mirrors; the supports also supply cooling water and electrical connections. Sources: http://www.nrel.gov/data/pix/Jpegs/13736.jpg

How Does the Color/Wavelength of Light Affect PV Efficiency? Test 5-8 colors using different backgrounds on PowerPoint Slides Purple Blue Green Yellow Orange Red White

Approximate Wavelength: 390-455 nanometers

Approximate Wavelength: 455-492 nanometers

Approximate Wavelength: 492-577 nanometers

Approximate Wavelength: 577-597 nanometers

Approximate Wavelength: 597-622 nanometers

Approximate Wavelength: 622-780 nanometers