Steady funds from the government and the pouring support of investors have lead to innovations in solar energy’s infinite potential. One of the companies currently working in this arena is MES Power who also specialise in high voltage power engineering and wind turbine hookups. There are three solar energy active conversions: solar photovoltaic, concentrated solar power, and solar heating and cooling.
Photovoltaic panels use silicon solar panels to convert the sun’s radiation to electrical energy. PV cells can be installed according to electricity needs and can power small devices like calculators and watches to a whole residential power requirement. There are also two kinds of photovoltaic panels: crystalline silicon (c-Si) modules and thin film modules.
C-Si modules. The majority of PV modules are based in crystalline silicon due to abundant resources. There are two main forms of c-Si: single-c-Si module and mc-Si or multi-crystalline silicon module. Commercial sc-Si converts electricity better than mc-Si while the latter is less expensive than single crystalline silicon modules.
Thin film modules Thin film PV modules are made by depositing extremely thin layers of photosensitive materials in glass, plastic, or stainless steel backing. The first thin film produce is a-Si or amorphous silicon. It offers several advantages including low consumption of raw materials, high production and automation efficiency, better performance in high ambient temperature, simple assembly and manufacturing integration, and more resistant to overheating. On the other hand, thin film modules have lower efficiency than crystalline silicon modules and the industry is yet to develop modules with long-term reliability.Underway research is the integration of single-crystalline and amorphous PV cells. The study aims to better the efficiency of thin film modules in the following years.
Photovoltaic technology is a reliable source of electricity to residential and commercial users due to the effective supporting policies and remarkable cost reduction. Emerging technology include concentrating photovoltaic and organic solar cells. Concentrating PV utilizes an optical concentrator system that focuses sunlight into a small efficiency cell. It is currently ongoing test stages on pilot applications.Concentrated solar power CSP concentrates energy from the sun’s rays to heat a thermal receiver suitable to hold high temperatures. Unlike a photovoltaic system where sunlight is converted to electricity, the thermal receiver converts sunlight to heat where it will be transported to a steam generator to convert it to electricity.
Concentrated solar power has been in operation for almost two decades and is a proven solar energy technology. It is not as marketable and simple as PV modules but the government of United States and Spain supported the technology to respond to the global crisis. CSP are mostly used by large power grid companies as it can collect and generate more electricity than PV panels. There are four current CSP technologies categorized in their ability to focus the sun’ rays and receive the sun’s energy: parabolic troughs, parabolic dishes, linear Fresnel collectors, and Towers or CRS.
Parabolic troughs consist of two parallel lines of mirror or reflector curved in a single direction to focus the sun’s energy to a fluid carrying receiver placed in the heart of the curved trough mirror. The sun’s energy heat the fluid inside the tube and the generated heat energy is used to generate electricity using a steam engine or generator. The tubes or absorber collectors are generally made of stainless steel and coated with a selective coating. Both the reflector and absorber collector moves with the sun as it crosses the sky. This ensures that the sun is continually focused on the receiver pipes. Parallel lines of parabolic troughs are called collector fields.Parabolic trough plants are hybrid. When there is insufficient sunlight, the plants burn natural gas such as coal and fuel to meet load requirements.
Parabolic dish plants use dish mirrors to concentrate sunlight and focus it to a thermal receiver. Unlike parabolic troughs, parabolic dish is a standalone unit, which is composed of a collector, thermal receiver, and an engine. The entire unit tracks the sun all throughout the day. The engine eliminates the need for heat transfer fluid and cooling water. Instead, the engine or generator is air-cooled. Parabolic dish uses dual axis collectors, allowing it to capture maximum amount of sunlight during the day. Compared to other CSP technologies, parabolic dishes offer the highest solar energy to electricity conversion as it can achieve extremely high temperatures and high efficiencies.
One of the drawbacks of small parabolic dishes is it does not work well with thermal storage. The converted electricity must be fed immediately to solar grids. However, very large parabolic dishes are found to be more compatible with thermal storage and natural gas back-up. Manufacturers as well as promoters see huge parabolic dishes to compete with larger solar thermal plants in the future.
Linear Fresnel Reflectors: This CSP technology is much like parabolic troughs as it uses a single axis collector and a fluid-carrying receiver. However, linear Fresnel collectors are made of long rows of ground mounted mirrors or reflectors to concentrate the sun’s rays. The thermal receiver is elevated and fixed atop the reflectors. Although the design has lower efficiency than parabolic troughs, it requires less land and is also more inexpensive than troughs. The current design of LFRs made possible direct steam generation by allowing water to be fed directly on the thermal receiver and be boiled at about 50 bars of atmospheric pressure. The saturated steam produced is use to power a steam cycle. LFRs produce lower optical efficiency compared to troughs and are low in compatibility with thermal storage.
Power Towers Also known as central receiver systems, power towers employ thousands of field tracking reflectors, heliostats, to collect sun’s radiation. The reflectors are mounted atop a fixed tower. Sunlight is absorb molten salt or pressurized water, working the fluid flowing through the receiver and serving as thermal storage as well. Power towers surpassed the operating temperature of parabolic troughs and linear Fresnel reflectors but not parabolic dishes. Power tower design offers more flexibility as designers can choose a wide array of heliostats, thermal storage, power blocks, and transfer fluids. This CSP technology has more potential for lower operating costs than line-focus technologies like parabolic troughs and LFRs.PV panels or CSPPV panels are more marketable and available to end-users. However, CSP is considered more cost-effective than photovoltaic panels. CSP can convert 60 – 80% of the sun’s rays to electricity while PV panels can only convert 10 – 15% of sunlight to grid compatible electricity.
PV panels’ energy generation can be scarce as it is limited to the amount of sunlight whereas CSP reigns supreme especially in desert locations. On the other hand, the simplicity and availability of PV panels make it a more viable solution than CSP that is yet to make its mark on the market. With the progression of solar energy technology, there is a great possibility of combining PV panels with CSP technology as demand for green energy increases steadily in different parts of the world.Solar thermal energy (STE) Solar thermal energy is the harnessing of sunlight and utilized it in specific purposes such as heating/cooling water or building spaces.
Unlike PV panels, solar thermal collectors convert heat to thermal energy so it can be used as a heating and cooling facility. Solar thermal collectors are categorized in low, medium, and high collectors. Low thermal collectors can heat swimming pools using flat plates that are similar to PV panels. Medium thermal collectors are used for both residential and commercial use and also utilize flat plates. High thermal collectors use CSP technology as it can convert heat better than flat plates. It is use in general power production. Concentrated solar power is a technique employed by solar thermal plants.
Residential and commercial users generally install low solar thermal collectors as a heating facility for swimming pools. A simple solar thermal heater can be composed of a series of black painted pipes layered in an insulated box and framed with glass, plastic, or metal panels. Potable water runs through these collectors and into the storage tank. Potable water can be cycled several times into the collectors and back to the tank again to increase water temperature. Thermosyphon system uses this configuration. The tank is placed above the collectors and takes advantage of the hot water’s natural tendency to rise above cold water. As hot water is drawn out for use, untreated potable water is fed through the collector.Water tanks under the collector need an electric pump to drive the water inside the collector. Such a system needs an anti-freeze or anti-corrosive chemical to treat the circulating fluid. A heat transfer fluid is also required to heat the end-users water supply.
Cheap Space heating and cooling
Low temperature collectors are also use for space heating. This is necessary in colder parts of the world, especially during winter season. Huge quantity of electricity is needed and if the building is well designed for solar insulation, a building can be cost and fuel-efficient and can provide a comfortable habitat.A simple solar space heating configuration is the installation of a Trombe wall. This is an enormous black painted wall and has a double glazed skin to prevent the sun’s heat from escaping. UTC or unglazed transpired collectors are perforated sun-facing walls used for pre-heating ventilation. Transpired collectors’ short payback period of 3 to 12 years makes it a cost-effective alternative to Trombe wall and other glazed collector systems.
Space cooling is not as technical as space heating and can be done through natural methods like planting deciduous trees. The leaves serve as shade during summer and its branches and limbs let the warmth of light pass through during winter. Other cooling solutions include installation of dome roofs and thermally massive structures, shaded windows, and bamboo structures. For mechanical space cooling methods, use of absorption refrigeration cycles and desiccant cycles are proven methods to promote a cooler space.
Cheap Solar cooking: This technology has been used for years in developing countries. A solar cooker is composed of wooden box lined with insulation and covered with a reflector. The reflector concentrates the heat of the sun to the pots, which are painted black to maximize heat absorption. The cooking time is relatively slower but is compensated by the lack of fuel cost. This cooking method is normally used in regions with strong and sufficient sunlight.
The Scheffler solar cooker configuration is much like concentrated solar power (CSP) as it uses a parabolic dish with a single axis tracking the course of the sun throughout the day. Since the reflector system has a focal point, it can reach high temperatures, allowing faster cooking time. Larger Scheffler solar cookers have been in production since 2008.Solar drying Solar thermal energy can be used to dry crops, woods, and food products like grains, fruits, and fish. Solar drying is a low cost solar thermal technology that uses transpired plate air collectors that are based on black materials or fabric. It is also environmentally friendly and improves the quality of the crops with minimal cost.
Solar water distillation: This is useful in regions where clean water is not always available. Solar thermal collectors heat the potable water where it evaporates and condenses at the bottom of the covering glass.Wind and Solar Energy: Compatible Hybrids of Two Alternative Energy Sources Solar power is a renewable energy resource but its intermittent nature makes it difficult to provide stable and reliable power that meets the required electricity demand. The inevitable change of seasons and weather conditions limit the amount of sunlight in various regions. Due to this, most residential and commercial solar power users use substantial backup in the form of fuel and coal powered electric grids, as solar power system cannot generate sufficient energy for the whole year. Combination of two alternative energy systems in a strategic location also reinforces the autonomy of the system.Low cost production of wind energy positively reduces the overall cost of solar and wind power system combination.
Wind energy is also one of the major sources of alternative energy and investor’s support for wind power generation exceeded other alternative energy sources. It also comes second for overall renewable energy generation in the world with hydro-power placing as the number one renewable energy resource.The federal government is pushing the use of combined solar and wind energy to answer the limitations of solar energy.
The plan is concentrated on regions where there are strong winds at night and ample sunlight during the day. This includes locations near mountains and the ocean or sea like rural and wider geographic areas. The combination of solar and wind energy is a proven alternative energy tandem as most of the time, there are strong gusts of wind at night when solar panels cannot collect and generate energy from the sun. Instead of using grid-tied electricity, wind energy serves as the backup energy generator as well as another electricity contributor to independent electric systems. There may still be a need for base load power but it would only be minimal.