solar energy

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History of Solar Thermal With an abundance of solar energy - enough shining on the Earth every hour to meet the world demand for an entire year - it's no surprise that solar radiation has time and again been harnessed to meet the growing needs of mankind. From ancient Mediterranean homes built to face the sun during the cold winter months to highly sophisticated thin-film photovoltaic cells, which generate electricity from sunlight, solar energy continues to be a leading source of alternative energy. In 1912, these parabolic solar collectors, built on a small farming community on the Nile River 15 miles south of Cairo, Egypt, were developed by a Philadelphia inventor, entrepreneur, and solar visionary named Frank Shuman. Each collector was 204 feet in length, 13 feet in width and was fitted with a mechanical tracker which kept it automatically tilted to appropriately absorb the sun. The heat collected by these reflectors was used to produce steam to power a series of large water pumps. Together they produced the equivalent of 55 horsepower and were capable of pumping an astonishing 6000 gallons of water per minute, bringing irrigation water to vast areas of arid desert land. After the war, as the world discovered the vast oil fields in Iraq, Iran, and Venezuela, the allure of limitless solar energy was diminished and Shuman returned to his hometown of Tacony, in Pennsylvania, never to realize his dreams and visions. Solar radiation, an emission-free and inexhaustible supply of energy, is the most abundant of all known energy sources in the world. Utilizing solar technology and other forms of renewable energy helps to reduce reliance on fossil fuels for energy production, thus directly reducing CO 2 emissions which contribute to artificial climate change and global warming. Solar Thermal - How Solar Water Heaters Work 1.Thermal Collectors: Heat Pipes & Evacuated Tube Technology The operation of the solar collector is as follows: 1. Solar Absorption: Solar thermal energy is absorbed within the evacuated tubes and is converted into usable concentrated heat. 2. Solar Thermal Transfer: Copper heat pipes transfer the thermal energy from within the solar tube into the copper header. 3. Solar Thermal Storage: A thermal transfer solution (water or glycol mixture) is pumped through the copper header. As the solution circulates through the copper header the temperature is raised by 5-10 °C / 9-18 °F.  Evacuated Tubes: The most efficient thermal collector on the market, the glass tubes absorb solar thermal energy for use in water heating. The tubes have a double wall, the area between the inner and outer layers of the wall are evacuated ( a vacuum). This acts as a thermos to keep heat from escaping into the atmosphere.   The evacuated tubes are glass tubes manufactured from strengthened borosilicate glass. The tubes have a double outer layer; the outer layer is fully transparent to allow solar energy to pass through unimpeded. The inner layer is treated with a selective optical coating which causes energy absorption without reflection. The inner and outer layer are fused at high temperatures at the end leaving an empty space between the inner and outer layers. All air is pumped out of the space between the two layers (evacuation process) creating the thermos effect which stops conductive and convective transfer of heat which might otherwise escape into the atmosphere. Heat loss is further reduced by the low-emissivity nature of the type of glass that is used. Heat Pipe: Inside the glass tube is the copper heat pipe. It is a sealed hollow copper tube that contains a small amount of proprietary liquid, which under low pressure boils at a very low temperature. In fact the liquid contained in the heat pipe boils at only 86 °F (30 °C). This heat pipe rapidly and efficiently transfers the captured thermal energy through the evacuated tube and delivers it to the manifold (header) as the liquid boils and rises. As the heat is removed from the heat pipe by the copper header, the liquid condenses and gravity returns it to the base of the heat pipe so that the process is continually repeated. Because the evacuated tubes are round, they serve as a passive tracking solar collector maximizing their performance. 2. Solar Heat Exchanger Tanks  • Brass valves and components • Includes temperature and pressure relief valve • Collector feed and return fittings located at front of tank for convenient installation • Highly efficient tank design • Highly efficient heating element • Prolonged tank life due to specially designed inner tank lining that resists corrosion • Copper tube heat exchanger • Bottom inlet for cold water to prevent mixing with hot water • Easily accessible inlets, outlets, valves and anode rod to quick install. • Automated temperature control valve • Temperature overheat protection. The solar heat exchanger tank stores 80 or 120 gallons of solar heated water depending on model selected. Typically the heat exchanger tank sits between the city/well water supply and the customers existing tank. When hot water is drawn from the existing tank, it is replaced by water from the solar tank that is already hot, meaning that the heating elements or gas burner of the existing tank do not have to operate. 3. Solar Pumping Station, Pumps & Controllers Tying the collectors and the tank together is a system that consists of valves, a controller, and a pump. Options are available to configure the system using a pre-configure pump-station (left), or design it with best-of-breed components (right). Our installers use both methods, depending on the application. Solar Controllers, Solar Water Pumps  SPP Solar Pump Station The SPP iSolar Differential Controllers and Solar Pump Stations are available in various configurations and also sold separately. Consult your sales engineer for the combination that is right for your system. The SPP iSolar Controller can be integrated with the SPP Pump Station giving it that “appliance look”. The SPP Pump Station is a pre-assembled unit designed for transferring heat from solar thermal collectors to a storage tank. These pump stations are used on the primary circulating loop of solar hot water heating systems to control the temperature of the water in the storage tank. The pump inside the unit is activated by the signal from the differential controller, which is inset into the pump station. The unit contains functional and safety devices for optimal control of solar water heating, and are available with a return connection only. Design Features: Check valve to prevent thermo circulation-Valves for flushing, filling, and emptying the system-Flow control valve with flow meter for displaying and setting the flow rate-In line thermometer for displaying return temperatures-Pressure gauge for displaying the system pressure-Safety relief valve to prevent overpressure-Three-speed Wilo solar pump for wide range of flow rates. The SPP iSolar Controllers come in 4 different models and feature multi-functional temperature control with additional functions available depending on model. The controllers can be used for a wide variety of applications and has inputs for four PT-1000 sensors. Preset factory defaults are defined for control of a solar water heating system, and have a built in second relay (some models) to divert any surplus heat that may be generated by the solar thermal collectors. The auxiliary relay can also be used to maintain tank temperature, protect the system from overheating, or divert the excess heat to another source. This controller features a large Liquid Crystal Display (LCD) screen & user interface, complete with three function keys. The easy-to-use icons assist both end-users and installers to operate, diagnose, and customize a solar heating system. System Screen LCD Display with 16-segment display & 8 symbols for system status - Operating LED control lamp and 3 push-button control -Δ T Control -Maximum tank temperature control -Heat generation measurement kWh (BTU)-Two relay models feature various advanced control options. The SPP iSolar controller (below) is integrated into the pump station.   Best Of Breed Solar Pump and Controller Solutions  Another option is to let us help you create a engineered solution for your specific application by combining a Steca solar controller with a custom design including the necessary pumps, valves and fittings. Solar Panels Plus keeps an inventory of most BOS (Balance of System) items and can assist you in determining the best solution for your customer. Our goal is to ship you everything you need along with your collectors, in one pre-engineered package. *The Steca Controller is typically used to run the circulation pump. The valve used for diverting the water/glycol mixture is controlled by a SPP-provided proprietary circuit. *The SPP iSolar Controller is typically used when the pump station is requested due to it's integrated design with the station. It also has a secondary relay which can be used to control an additional pump or valve. In addition to the above solutions for residential of small commercial use, SPP can provide custom PLC controllers for larger commercial and industrial projects.