- the parabolic trough,
- the concentrating linear fresnel reflector,
- the Stirling dish
- and the solar power tower.
The production of electricity with solar energy has been an ongoing area of research for The Founder and Principal Engineer since his days as a Graduate Student at the University of Alberta, in Edmonton, Alberta, Canada. Since the amount of energy which impinges on the earth every day is immense, it has been the dream of every electrical engineering student to harness this mostly untapped energy resource.
However the stark reality is that after 40 years of effort in this industry, the results have been disappointing. There are many reasons why this vast energy resource remains untapped. The main reason is the lack of a coordinated effort to develop cheap energy storage devices and facilities.
This page will serve as the introduction to our Solar Energy Portfolio of Intellectual Properties relating to the production of electricity with Solar Energy. The majority of our research effort is directed towards energy storage devices and broadening the bandwidth of solar cells into the infrared and ultraviolet.
Section one of this page will discuss techniques for the concentration of Solar Energy to create utility size projects. The reason this technique is placed in the first position has to do with the overall efficiency of the process. Section two will concentrate on the more familiar photovoltaic aspects of Solar Energy Conversion to electricity.
SECTION ONE: CONCENTRATING SOLAR POWER
Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power plant. A wide range of concentrating technologies exists: the most developed are:
Various techniques are used to track the sun and focus light. In all of these systems a working fluid is heated by the concentrated sunlight, and is then used for power generation or energy storage.
1. The Parabolic Trough: A parabolic trough consists of a linear parabolic reflector that concentrates light onto a receiver positioned along the reflector’s focal line. The receiver is a tube positioned right above the middle of the parabolic mirror and is filled with a working fluid. The reflector is made to follow the sun during daylight hours by tracking along a single axis. Parabolic trough systems provide the best land-use factor of any solar technology. The SEGS plants in California and Acciona’s Nevada Solar One near Boulder City, Nevada are representatives of this technology.
2. The Concentrating Linear Fresnel Reflector: Compact Linear Fresnel Reflectors are CSP-plants which use many thin mirror strips instead of parabolic mirrors to concentrate sunlight onto two tubes with working fluid. This has the advantage that flat mirrors can be used which are much cheaper than parabolic mirrors, and that more reflectors can be placed in the same amount of space, allowing more of the available sunlight to be used. Concentrating linear fresnel reflectors can be used in either large or more compact plants.
3. The Sterling Solar Dish: The Stirling solar dish combines a parabolic concentrating dish with a Stirling engine which normally drives an electric generator. The advantages of Stirling solar over photovoltaic cells are higher efficiency of converting sunlight into electricity and longer lifetime. Parabolic dish systems give the highest efficiency among CSP technologies. The 50 kW Big Dish in Canberra, Australia is an example of this technology.
4. The Solar Power Tower: A solar power tower uses an array of tracking reflectors (heliostats) to concentrate light on a central receiver atop a tower. Power towers are more cost effective, offer higher efficiency and better energy storage capability among CSP technologies. The PS10 Solar Power Plant and PS20 solar power plant are examples of this technology.
SECTION TWO: PHOTOVOLTAICS
A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current using the photoelectric effect. The first solar cell was constructed by Charles Fritts in the 1880s. The German industrialist Ernst Werner von Siemens was among those who recognized the importance of this discovery, In 1931, the German engineer Bruno Lange developed a photo cell using silver selenide in place of copper oxide, although the prototype selenium cells converted less than 1% of incident light into electricity. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4.5–6%.
Photovoltaic power systems produce direct current (DC) power which fluctuates with the sunlight’s intensity. For practical use this usually requires conversion to certain desired voltages or alternating current (AC), through the use of inverters. Multiple solar cells are connected inside modules. Modules are wired together to form arrays, then tied to an inverter, which produces power at the desired voltage, and for AC, the desired frequency/phase.
Many residential systems are connected to the grid wherever available, especially in developed countries with large markets. In these grid-connected PV systems, use of energy storage is optional. In certain applications such as satellites, lighthouses, or in developing countries, batteries or additional power generators are often added as back-ups. Such stand-alone power systems permit operations at night and at other times of limited sunlight.
HISTORY OF SOLAR TECHNOLOGIES
Development and deployment
The early development of solar technologies starting in the 1860s was driven by an expectation that coal would soon become scarce. However, development of solar technologies stagnated in the early 20th century in the face of the increasing availability, economy, and utility of coal and petroleum. In 1974 it was estimated that only six private homes in all of North America were entirely heated or cooled by functional solar power systems. The 1973 oil embargo and 1979 energy crisis caused a reorganization of energy policies around the world and brought renewed attention to developing solar technologies. Deployment strategies focused on incentive programs such as the Federal Photovoltaic Utilization Program in the US and the Sunshine Program in Japan. Other efforts included the formation of research facilities in the US (SERI, now NREL), Japan (NEDO), and Germany (Fraunhofer Institute for Solar Energy Systems ISE.
Between 1970 and 1983 photovoltaic installations grew rapidly, but falling oil prices in the early 1980s moderated the growth of PV from 1984 to 1996. Since 1997, PV development has accelerated due to supply issues with oil and natural gas and the improving economic position of PV relative to other energy technologies. Photovoltaic production growth has averaged 40% per year since 2000 and installed capacity reached 39.8 GW at the end of 2010, of them 17.4 GW in Germany. The Desert Sunlight Solar Farm is a 550 MW solar power plant built, on Federal Land, in Riverside County, California, that uses thin-film solar photovoltaic modules made by First Solar.
At the end of September 2013, IKEA announced that solar panel packages for houses will be sold at 17 United Kingdom IKEA stores by the end of July 2014. The decision followed a successful pilot project at the Lakeside IKEA store, whereby one photovoltaic (PV) system was sold almost every day. The panels are manufactured by a Chinese company named Hanergy Holding Group Ltd.
Photovoltaic systems use no fuel and modules are expected to have a life of 25 years. The cost of installation is almost the only cost, as there is very little maintenance required. Installation cost is measured in $/watt or €/watt. The electricity generated is sold for ¢/kWh. 1 watt of installed photovoltaics generates roughly 1 to 2 kWh/year, as a result of the local insolation. The product of the local cost of electricity and the insolation determines the break even point for solar power. The International Conference on Solar Photovoltaic Investments, organized by EPIA, has estimated that PV systems will pay back their investors in 8 to 12 years.
The declining price of PV has been reflected in rapidly growing installations. Additionally, governments have created various financial incentives to encourage the use of solar power, such as feed-in tariff programs. Also, Renewable portfolio standards impose a government mandate that utilities generate or acquire a certain percentage of renewable power regardless of increased energy procurement costs. In most states, RPS goals can be achieved by any combination of solar, wind, biomass, landfill gas, ocean, geothermal, municipal solid waste, hydroelectric, hydrogen, or fuel cell technologies.