Solar Thermal:
Solar thermal technologies rely on the sun's heat energy, which is considered to be one of the lowest quality energies, to produce something useful, whether it be heating for a building or electricity. There are three types of solar thermal collectors, low, medium, and high temperature systems.
Solar Thermal Energy Storage:
The storage of heat is very important for the running of CSP power plants so that they are capable of producing energy when there is lower than average solar irradiation, whether it be because of overcast skies or because it is night time. This allows the power plant to run more often, generating more electricity. This is an advantage over running very hard during the day and storing the energy as electricity to be used while the plant is shut down at night because heat is much cheaper and more efficient to store than electricity. Short term storage (about one hour) can be accomplished using pressurized steam, but more long term storage (on the order of a few hours to a couple days) can be accomplished using the technologies listed in long term storage under \"thermal\".
PV:
Chart at http://en.wikipedia.org/wiki/Photovoltaics (73) for detailed worldwide production in 2006
(check reference) also chart of PV plants
Add solar calculator from 401 to website? Uses of PVs:
- Solar power plants that produce electricity for the grid
- Building Integrated PhotoVoltaics (BIPV) that produce electricity for the buildings to which they are attached
- Transportation, either as auxilary for cars and boats or to efficiently produce hydrogen, possibility for use in hydrogen economy
- Standalone systems: Photovoltaics have been used for many years to power calculators and novelty devices. More recently, solar powered remote fixed devices have become more popular in settings such as with signs, parking meters, emergency telephones, remote lights, etc.
Life-cycle Energy Payback
Life-cycle energy paybacks look not at the lifetime monetary costs of a solar system, but instead the lifetime energy costs of the system. The Life-cycle energy payback is the amount of time it takes a solar system to produce as much energy as it took to produce it and keep it running. In 2000, this was estimated to be 8 to 11 years, but more recently, crystalline silicon PV systems have been estimated to have life-cycle energy paybacks closer to 1.5 to 3.5 years. Thin film technologies in Southern Europe are as low as 1-1.5 years. Given the fact that these systems have lifetimes of at least 30 years, the EROEI (Energy Return On Energy Investment), is in the range of 10 to 30, depending on the material used, how the system is constructed, and the geographic location of the system.
System Design
Solar cells are usually encapsulated in a module with a glass sheet on top to allow light through. The solar cells are usually connected in series in modules until they reach the desired voltage, and then in parallel to increase the voltage. The power output of this system is measured in kilowatts, with the total energy being in kilowatt-hours, the number of kilowatts produced times the number of hours it is produced for. The typical rule of thumb for how much energy a system will produce is that it will average 20% of the peak production every hour for 24 hours (obviously this is not how it actually occurs). Therefore, a 1 kilowatt panel will produce 4.8kWh/day (0.2kWh/hour * 24 hours/day).