Using thermal energy directly from sunlight is the oldest Renewable Energy use. People have heated homes this way for thousands of years -- typically called "Passive Solar".
More recently, a set of "Active Thermal Solar" technologies have been developed. The pictures at the right show the main "active" solar technogies used today. The top two pictures are concentrating solar colletors that create very hight temperatures and are used primarily for electric power generation. The second picture, concentrating parabolic trough, uses oil or molten salt as thermal transfer fluid. This type of very high temperature solar collector is also being used to reduce fossil fuel use in industry where it has been used for process heating and boiling water.
The third photo shows a typical residential or commercial flat plate soolar thermal collector used ainly for hot water (DHW) production and sometimes for radiant floors.
Batteries -- Electric Energy Storage Batteries
The latest addition to the RE/EE mix is Electric Batteries. Lead-acid batteries in off-grid RE systems for some time, but they are dangerous and have a limited life. New battery technologies have made are now making these batteries useful in other ways. An Electric Battery quite simply lets one use electricity at a time other than when it was generated. Without a battery, you have to use 100% of any generated electricity at the very moment it is produced. The most common RE/EE way to produce electricity is PV, but of course PV only generates electricity when the sun is shining. We need electricity 24 hours a day -- batteries make that possible.
Net Zero Economics
Net Zero means both "pollution-free" and "cost-free energy". This is the basic premise of the Net Zero Foundation -- that we can be pollution-free and make money doing it. The below graphic shows the basic economics of Renewable Energy systems -- this particular graphic shows how
technology B?". This is a completely erroneous question that comes mainly because to date the RE/EE world has been dominated by "technologies". We started Net Zero Foundation to overcome this RE/EE limitation by showing that Net Zero is the goal and the only goal, not a technology! The various RE/EEtechnologies involved are just tools to be applied as best they fit each site.
Thus, the only legitimate question now is "where do I start?" and "how fast should I implement these technologies?"
The key Net Zero technologies that a business or home owner can implement are PV, GHP, EE, and Batteries. We will go through each of these technologies in detail. The other Net Zero technologies, Hydro, Wind, GEO, and Nuclear are generally only implemented by utilities and large corporations.
PV - Photovoltaics
PV panels turn sunlight directly into electricity. The basic PV technology is a silica-based flat wafer similar to computer chips and LED technology, and manufactured in a similar factory. Early PV cells were "monocrystalline" and have been found to have a extremely long life, but they are also expensive to make and generally only used in remote locations where reliability is essential. The PV panels going on roofs and solar farms are "polycrystalline" cells and are far less expensive. PV installation cost in large installations is now about $2.50/Watt.
GHP - Geothermal Heat Pumps and Ground Energy Storate
GHP is a thermal energy technology that is the most efficient way to mechanically heat and cool any building. GHP is also a thermal energy storage technology, where the excess heat from cooling a building in the summer is stored in the earth for use heating the building the next winter. GHP is termed a Renewable Thermal technology because it uses a summertime recurring thermal energy source (waste heat from cooling) to later provide heating in the winter. This storage of thermal energy in the ground from one season to another is done with a Ground Heat Exchanger (GHEX) which involves special high-grade pipes buried in the earth. GHP can reduce the amount of power used for heating and cooling by a factor of 4x to 7x, and requires no fossil fuels.
EE -- Energy Efficiency
Energy Efficiency is the most basic energy conservation technology available. EE includes insulation, air leakage sealing, double-pane glass, low-e glass, etc. The slingle largest energy loss in a structure is typically air leakage. Newer EE technologies include spray foam insulation which provides both insulation from heat and cold, and also provides air leakage sealing.
Hydro -- Hydroelectric Dams
Hydroelectric power is one of the oldest RE/EE technologies. Electricity is generated by using the power of falling water to turn a large generator. The sun provides the renewable energy by evaporating the water for it to fall again as rain upstream from the dam. Hydro power is very efficient once a dam is built, but building new dams is very controversial because they cause large areas to be permanently flooded. Hydro power is also an energy storage technology because the energy is present once the water is behind the dam, and generation can be ramped up and down to match demand to some degree. However, the amount of energy that can be stored is limited by the size of the dam and lake volume behind the dam.
GEO - Deep Earth Geothermal
The inside of the earth is very hot -- so hot that the rock is molten. At many locations, this hot is close enough to the surface of the earth that we an drill wells near it. There are several methods
of using such high temperature wells to produce energy, including both thermal energy and electric energy. For example, the city of Boise, ID has operated a thermal well hot water district heating system for over 100 years. More recently, deep earth hot wells are being used to produce electricity as depicted in the photo at the right -- water is pumped down the well where it heated high enough to produce steam, which then powers a turbine to produce electricity.
Wind -- Electricity Generation
Wind energy has long been used for pumping water in all parts of the world. Most recently, Wind Power is being used for generating electricity. The photo at the right shows a typical large wind generator now geing used for utility-scale wind farms. There are areas of the earty where the wind blows very steadily for much of the year. West Texas and Oklahoma in the U.S. are examples of such "wind rich" locations. In these areas, farmers have begun to openly accept wind generators on their lands from which they are making a good living. The wind in so plentiful in some locations that utilities have started offering wind generated electricity for free during some time periods.
We all know that Nuclear Power is somewhat dangerous and is thus not a great long term energy solution. There is also a very major issue of what to do with the "waste" radioactive materials from nuclear power plants -- a completely unresolved issue in the U.S.
However, Nuclear does provide us with non-GHG electricity. Therefore, Nuclear is one of the Net Zero Energy electric power production technologies we will utilize while the reactors still
exist. Several of the existing nuclear plants have already reached their maximum useful life and have been shut down, and some have been shut down because of public activism. And, no new nuclear plants are likely to be built because they are more expensive then the Wind/PV/GEO Renewable Energy technologies. Thus, we do not anticipate Nuclear will be a technology that leads us to the "Age of Free Energy", and we only include it with an Asterix in the name!