Solar Thermal Systems seek to store heat from the sun that can be used for a variety of purposes. Many different approaches can be employed here, including active systems, such as solar hot water heaters, and passive systems, in which careful engineering design results in a building that automatically stores and utilizes solar energy. Greenhouses are a prime candidate for passive solar design, in which they collect solar energy on sunny days in winter and utilize it to keep the house warm at night.
The main advantages of solar energy are that it is clean, able to operate independently or in conjunction with traditional energy sources, and is remarkably renewable. The main disadvantages are that it is currently more expensive than traditional energy, and the availability of solar radiation varies from day to day, and from season to season. In fact, some parts of Pennsylvania are among the cloudiest spots in the United States. In spite of this, there is still opportunity for using solar energy effectively in Pennsylvania.
Solar energy is lauded as an inexhaustible fuel source that is pollution and often noise free. The technology is also versatile. For example, solar cells generate energy for far-out places like satellites in Earth orbit and cabins deep in the Rocky Mountains as easily as they can power downtown buildings and futuristic cars.
But solar energy doesn't work at night without a storage device such as a battery, and cloudy weather can make the technology unreliable during the day. Solar technologies are also very expensive and require a lot of land area to collect the sun's energy at rates useful to lots of people.