1. Solar Water Heating AKA Solar Thermal

2. Solar Thermal vs Solar Photovoltaic Solar Photovoltaic(PV for short) • Converts sunlight into electricity • 20% efficient • 15,000 megawatts worldwide Solar Thermal • Directly heats fluid by solar radiation • 60% efficient • 450,000 megawatts worldwide

3. PV Cost and power output • Solar PV • $6-$7 per watt currently • A typical 3 KW system generates 5500 KwH per year and costs around $18,000 • 5500 KwH = roughly $550 dollars worth of electricity • 33 year payback(without subsidies) • Until recently subsidies in Austin($3.75 per watt) and the federal tax credit pushed the payback time to less than 10 years. • Some were getting “Free” systems in Austin

4. Solar thermal cost and power output • A standard electric water heater uses 400-800 KwH per year. Sometimes more. • A solar water heater can offset 80% or more of that cost. • Costs around $6000 • Payback 6-12 years depending on Home habits(showers, laundry, etc.) • Payback 2-4 years with subsidies in Austin • $2000 Austin Energy rebate • 30% federal tax credit

5. How it works • There are several different types • Open loop-most common, used in warm climates • Drainback-used in temperate climates • Glycol pressurized-used in temperate climates • Passive ICS Drainback Open Loop

6. DrainbackSytems • Preferred system in Texas climate • Panel must be located above drainback tank • Uses gravity to drain the panel during freezing spells • No glycol flushing required • Stores water at temperatures of 150+ degrees.

7. Cross section of the collector

8. Solar thermal worldwide • Worldwide, Solar thermal produces 30 times as much energy as solar PV at a fraction of the cost. • Over 90% of the homes in Israel and Cyprus use solar water heating due to high energy costs • China has over 27 million rooftop solar water heaters. • Millions installed worldwide. Very common in Germany, Austria, the Middle East, the Bahamas, anywhere energy prices are high. • In the U.S., they are most common in Florida, California, and Hawaii • Solar water heating is now code required in: • Spain • Israel • Australia • Hawaii

9. Environmental Benefits • A standard water heater uses the equivalent of 11 barrels of oil per year • Equal to the fuel consumption of a small car • A gas water heater uses 250 therms per year. That’s 250,000 cubic feet of natural gas. • In 2005, worldwide, solar water heating offset: • 70 million barrels of oil • 29 million tons of carbon emissions