Solar Power:
All research was conducted online on July 30, 2012 in the UTSA ITEC computers.

Active Solar Heating

There are two basic types of active solar heating systems based on the type of fluid—either liquid or air—that is heated in the solar energy collectors. (The collector is the device in which a fluid is heated by the sun.) Liquid-based systems heat water or an antifreeze solution in a "hydronic" collector, whereas air-based systems heat air in an "air collector."
Both of these systems collect and absorb solar radiation, then transfer the solar heat directly to the interior space or to a storage system, from which the heat is distributed. If the system cannot provide adequate space heating, an auxiliary or back-up system provides the additional heat. Liquid systems are more often used when storage is included, and are well suited for radiant heating systems, boilers with hot water radiators, and even absorption heat pumps and coolers. Both air and liquid systems can supplement forced air systems.

Economics and Other Benefits of Active Solar Heating Systems

Active solar heating systems are most cost-effective when they are used for most of the year, that is, in cold climates with good solar resources. They are most economical if they are displacing more expensive heating fuels, such as electricity, propane, and oil heat. Some states offer sales tax exemptions, income tax credits or deductions, and property tax exemptions or deductions for solar energy systems.
The cost of an active solar heating system will vary. Commercial systems range from $30 to $80 per square foot of collector area, installed. Usually, the larger the system, the less it costs per unit of collector area. Commercially available collectors come with warranties of 10 years or more, and should easily last decades longer. The economics of an active space heating system improve if it also heats domestic water, because an otherwise idle collector can heat water in the summer.
Heating your home with an active solar energy system can significantly reduce your fuel bills in the winter. A solar heating system will also reduce the amount of air pollution and greenhouse gases that result from your use of fossil fuels such as oil, propane, and natural gas for heating or that may be used to generate the electricity that you use.

Selecting and Sizing a Solar Heating System

Selecting the appropriate solar energy system depends on factors such as the site, design, and heating needs of your house. Local covenants may restrict your options; for example homeowner associations may not allow you to install solar collectors on certain parts of your house (although many homeowners have been successful in challenging such covenants).
The local climate, the type and efficiency of the collector(s), and the collector area determine how much heat a solar heating system can provide. It is usually most economical to design an active system to provide 40%–80% of the home's heating needs. Systems providing less than 40% of the heat needed for a home are rarely cost-effective except when using solar air heater collectors that heat one or two rooms and require no heat storage. A well-designed and insulated home that incorporates passive solar heating techniques will require a smaller and less costly heating system of any type, and may need very little supplemental heat other than solar.
Besides the fact that designing an active system to supply enough heat 100% of the time is generally not practical or cost effective, most building codes and mortgage lenders require a back-up heating system. Supplementary or back-up systems supply heat when the solar system cannot meet heating requirements. They can range from a wood stove to a conventional central heating system.

Controls for Solar Heating Systems

Controls for solar heating systems are usually more complex than those of a conventional heating system, because they have to analyze more signals and control more devices (including the conventional, backup heating system). Solar controls use sensors, switches, and/or motors to operate the system. The system uses other controls to prevent freezing or extremely high temperatures in the collectors.
The heart of the control system is a differential thermostat, which measures the difference in temperature between the collectors and storage unit. When the collectors are 10°–20°F (5.6°–11°C) warmer than the storage unit, the thermostat turns on a pump or fan to circulate water or air through the collector to heat the storage medium or the house.
The operation, performance, and cost of these controls vary. Some control systems monitor the temperature in different parts of the system to help determine how it is operating. The most sophisticated systems use microprocessors to control and optimize heat transfer and delivery to storage and zones of the house.
It is possible to use a solar panel to power low voltage, direct current (DC) blowers (for air collectors) or pumps (for liquid collectors). The output of the solar panels matches available solar heat gain to the solar collector. With careful sizing, the blower or pump speed is optimized for efficient solar gain to the working fluid. During low sun conditions the blower or pump speed is slow, and during high solar gain, they run faster.
When used with a room air collector, separate controls may not be necessary. This also ensures that the system will operate in the event of utility power outage. A solar power system with battery storage can also provide power to operate a central heating system, though this is expensive for large systems.

world solar map



  • Fuel is not burned so there is minimal pollution
  • Water to run the power plant is provided free by nature
  • Hydropower plays a major role in reducing greenhouse gas emissions
  • Relatively low operations and maintenance costs
  • The technology is reliable and proven over time
  • It's renewable - rainfall renews the water in the reservoir, so the fuel is almost always there

  • High investment costs
  • Hydrology dependent (precipitation)
  • In some cases, inundation of land and wildlife habitat
  • In some cases, loss or modification of fish habitat
  • Fish entrainment or passage restriction
  • In some cases, changes in reservoir and stream water quality
  • In some cases, displacement of local populations
In 2006, 7% of the energy Americans consumed were renewable. Out of that 7%, 42% of it was hydropower.

Biomass is an organic renewable energy source that includes materials such as agriculture and forest residues, energy crops, and algae






Benefits of Geothermal Energy:
The biggest benefit of GHPs is that they use 25%–50% less electricity than conventional heating or cooling systems.

Geothermal heat pump systems allow for design flexibility and can be installed in both new and retrofit situations.
Problems of Geothermal Energy:

The main problem with geothermal, of course, is lack of easily accessible surface sites.

Note that Geothermal does pollute the environment with small amounts of sulfur and carbon emission but to date, the tapped sources are natural so this would happen anyway

Uses of Geothermal Energy:

In Texas

Geothermal Heat Pumps – Everywhere

Hydrothermal (Direct Use) of fluids (75 – 190°F)

Electricity generated from oil & gas well fluids


The worldwide application of geothermal energy for non-electric use is reviewed.
The oldest known spa is a stone pool on China’s Lisan mountain built in the Qin dynasty in the 3rd century BC, at the same site where the Huaqing Chi palace was later built. In the first century AD, Romans conquered //Aquae Sulis//, now Bath, Somerset, England, and used the hot springs there to feed public baths and underfloor heating. The admission fees for these baths probably represent the first commercial use of geothermal power.


Wind Energy


According to the U.S. Department of Energy's (DOE's) 2010 Wind Technologies Market Report U.S. wind power additions in 2010 experienced a reduction from the 2009 additions due to market conditions that mirrored the U.S. economy at large, with 5,113 megawatts of new capacity and $11 billion invested. New wind power projects contributed roughly 25% of the new nameplate capacity added to the U.S. electrical grid in 2010, compared to 42% in 2009, and 43% in 2008. For the fourth consecutive year, wind power contributed more than 25% of new nameplate capacity to the U.S. electrical grid.