Solar Thermal Energy:

Heating our homes while cooling our planet

Chris Mayor and Stephen Mizera

What is solar thermal energy?

A technology for harnessing solar energy for heat

Uses mirrors and lenses to concentrate sunlight onto heat collectors

Used to produce electrical power

Collectors

Can be categorized into three different types: Low-temperature, medium-temperature, and high-temperature

Used to concentrate and harness the power of the sun

Low-temperature Collector

Made up of flat plates Most often used in the heating of swimming pools Can use the sunlight to heat water for houses Began appearing in the United States in the 1890’s Thermal mass materials such as stone and cement can be used to

maintain comfortable temperatures within a household Another use of this is in evaporation ponds, where dissolved solids are

concentrated through evaporation Evaporation ponds are the oldest application of solar thermal energy

usage

Medium-Temperature Collector

Produces 50% of hot water needed for commercial and residential usage

A solar cooker is the most well known type of medium-temperature collector

Solar cookers use reflectors for concentrating light on a cooking container

Solar stills are used to disinfect water by extinguishing the chemicals in the water

High-Temperature Collector

When temperatures are above 95 degrees Celsius, flat plate collectors are used without concentrating the solar rays

The types of collectors vary with how high the temperature is

Steam and gas turbines are the most prevalent

Types of System Designs for High-Temp Collectors

Parabolic trough designs: direct solar radiation goes to receivers at focal point of parabolic curve

Power Tower: use movable, flat mirrors to focus the sun’s rays on the receiver of the tower

Dish designs: use one large, parabolic dish to focus the sunlight into a receiver

Fresnel Reflectors: long, narrow, shallow-curvature mirrors focus the sun’s rays onto receivers

Fresnel Lenses: not in use currently; cheaper than mirrors for Fresnel Reflectors

MicroCSP: designed mainly for rooftop installation

Benefits of Solar Thermal Energy

The sun produces large and unlimited quantities of energy The sun delivers about 300 BTUs per square foot to anything on the

earth’s surface that is facing it directly on a clear day Solar radiation arrives on the surface of the earth with a maximum

power of approximately 1 kilowatt per square meter (kW/m2). Easily harnessed by many different types of collectors.

Disadvantages of Solar Thermal Energy

Only certain regions of the world receive adequate amounts of direct sunlight

Difficulty in storage of heat Costs a large amount of money to produce the

materials necessary to harness the energy Solar thermal energy plants can harm desert

ecosystems if not properly managed Solar thermal energy farms require a large amount

of space

Financial Impacts of Solar Thermal Energy

Because it does not rely on fuel, costs consist mainly of constructing plants

Minor operational and maintenance costs Tax incentives for installing solar thermal

systems

Environmental Impacts of Solar Thermal Energy

Produces no air or water pollution in the process of harnessing it

Takes up a lot of much needed space in the desert for the farms

Creates some indirect impacts to environment, such as manufacturing the photovoltaic cells used to convert sunlight into electricity, consumes silicon and produces some waste products

Progress of United States in producing solar thermal energy

Currently, the United States does not utilize solar thermal energy as a major energy source

Less money will be used to buy oil for gas, which will make the United States less dependent on foreign oil

Statistics on Solar Thermal Energy

Statistics on Solar Thermal Energy (cont.)

Solar Thermal Collector Average Price, 1997-2006

Statistics on Solar Thermal Energy (cont.)

Low-temperature collectors contributed 75% of the total shipments of collectors in 2006, medium-temperature collectors 6.5%, and high-temperature collectors 18.5%

Largest gain in market share from 2005 to 2006 was high-temperature collectors, which went from nearly a negligible amount of shipments to 18.5% of the total collector shipments

Total shipment revenue nearly tripled from $45.8 million in 2005 to $121.1 million in 2006