Solar Water Heating AKA Solar Thermal Solar Thermal

Solar Water Heating AKA Solar Thermal

Solar Thermal vs 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

PV Cost and power output �Solar PV �$6 -$7 per watt currently �A typical 3 KW system generates 5500 Kw. H per year and costs around $18, 000 � 5500 Kw. H = 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

Solar thermal cost and power output �A standard electric water heater uses 400 -800 Kw. H 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

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

Drainback Sytems �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.

Cross section of the collector

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

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