31-03-2011, 01:00 PM
My name is Daniel, i need a project article on solar water heater.
31-03-2011, 01:00 PM
My name is Daniel, i need a project article on solar water heater.
27-09-2012, 04:57 PM
SOLAR WATER HEATER
solar water heater.docx (Size: 1.14 MB / Downloads: 59) INTRODUCTION:- Solar water heating or solar hot water is water heated by the use of solar energy. Solar heating systems are generally composed of solar thermal collectors, a fluid system to move the heat from the collector to its point of usage. The system may use electricity for pumping the fluid, and have a reservoir or tank for heat storage and subsequent use. The systems may be used to heat water for a wide variety of uses, including home, business and industrial uses. Heating swimming pools, underfloor heating or energy input for space heating or cooling are more specific examples. In many climates, a solar heating system can provide up to 85% of domestic hot water energy. This can include domestic non-electric concentrating solar thermal systems . Residential solar thermal installations can be subdivided into two kinds of systems: compact and pumped systems. Both typically include an auxiliary energy source (electric heating element or connection to a gas or fuel oil central heating system) that is activated when the water in the tank falls below a minimum temperature setting such as 50 °C. Hence, hot water is always available. The combination of solar water heating and using the back-up heat from a wood stove chimney to heat watercan enable a hot water system to work all year round in cooler climates, without the supplemental heat requirement of a solar water heating system being met with fossil fuels or electricity. Among pumped options, there is an important distinction to be made regarding the sustainability of the design of the system. This relates to what source of energy powers the pump and its controls. The type of pumped solar thermal systems which use mains electricity to pump the fluid through the panels are called low carbon solar because the pumping negates the carbon savings of the solar by about 20%, according to data in a report called "Side by side testing of eight solar water heatings" by DTI UK. However, zero-carbon pumped solar thermal systems use solar electricity which is generated onsite using photovoltaics to pump the fluid and to operate its control electronics. This represents a zero operational carbon footprint and is becoming an important design goal for innovative solar thermal systems. HISTORY:- Flat-plate collectors for solar water heating were popular in Florida and Southern California in the 1920s. Levi Yissar built the first prototype Israeli solar water heater and in 1953 he started NerYah Company, Israel's first commercial manufacturer of solar water heaters.[4][5] Despite the abundance of sunlight in Israel, solar water heaters were used by only 20% of the population by 1967. Following the energy crisis in the 1970s, in 1980 the Israeli Knesset passed a law requiring the installation of solar water heaters in all new homes (except high towers with insufficient roof area). As a result, Israel is now the world leader in the use of solar energy per capita with 85% of the households today using solar thermal systems (3% of the primary national energy consumption). During this time, there was some resurgence of interest in solar heating in North America. Technical innovation has improved performance, life expectancy and ease of use of these systems. Installation of solar water heating has become the norm in countries with an abundance of solar radiation, like Cyprus, Israel and Greece, as well as in Japan and Austria, where there is less. In 2005, Spain became the first country in the world to require the installation of photovoltaic electricity generation in new buildings, and the second (after Israel) to require the installation of solar water heating systems in 2006. Australia adopted the mandatory regulation for solar thermal for new construction in 2006 as well. TECHNIQUE:- In order to heat water using solar energy, a collector is fastened to the roof of a building, or on a wall facing the sun. In some cases, the collector may be free-standing. The working fluid is either pumped (active system) or driven by natural convection (passive system) through it. The collector could be made of a simple glass topped insulated box with a flat solar absorber made of sheet metal attached to copper pipes and painted black, or a set of metal tubes surrounded by an evacuated (near vacuum) glass cylinder. In some cases, before the solar energy is absorbed, a parabolic mirror is used to concentrate sunlight on the tube. Some systems are capable of converting light to heat and therefore are not as reliant on outside temperature. A simple water heating system would pump cold water out to a collector to be heated, the heated water flows back to a collection tank. This type of collector can provide enough hot water for an entire family. Heat is stored in a hot water tank. The volume of this tank will be larger with solar heating systems in order to allow for bad weather, and because the optimum final temperature for the absorber is lower than a typical immersion or combustion heater. The working fluid for the absorber may be the hot water from the tank, but more commonly (at least in pumped systems) is a separate loop of fluid containing anti-freeze and a corrosion inhibitor which delivers heat to the tank through a heat exchanger (commonly a coil of copper tubing within the tank). Another lower-maintenance concept is the 'drain-back': no anti-freeze is required; instead all the piping is sloped to cause water to drain back to the tank. The tank is not pressurized and is open to atmospheric pressure. As soon as the pump shuts off, flow reverses and the pipes empty by the time when freezing could occur. Economics, energy and system costs:- In sunny, warm locations, where freeze protection is not necessary, a batch type solar water heater can be extremely cost effective. In higher latitudes, there are often additional design requirements for cold weather, which add to system complexity. This has the effect of increasing the initial cost (but not the life-cycle cost) of a solar water heating system, to a level much higher than a comparable hot water heater of the conventional type. When calculating the total cost to own and operate, a proper analysis will consider that solar energy is free, thus greatly reducing the operating costs, whereas other energy sources, such as gas and electricity, can be quite expensive over time. Thus, when the initial costs of a solar system are properly financed and compared with energy costs, then in many cases the total monthly cost of solar heat can be less than other more conventional types of hot water heaters (and also in conjunction with an existing hot water heater). At higher latitudes, solar heaters may be less effective due to lower solar energy, possibly requiring dual-heating systems. In addition, federal and local incentives can be significant. Compact systems (passive systems) :- A compact system also known as a monobloc has a tank for the heated water and a solar collector mounted on the same chasis. Typically these systems will function by natural convection (thermosiphon) or heatpipes to transfer the heat energy from the collector to the tank. A special type of compact system is the Integrated Collector Storage (ICS or Batch Heater) where the tank acts as both storage and solar collector. Batch heaters are basically thin rectilinear tanks with glass in front of it generally in or on house wall or roof. They are seldom pressurised and usually depend on gravity flow to deliver their water. They are simple, efficient and less costly than intense plate and tube collectors but only suitable in moderate climates with good sunshine. A step up from the ICS is the Convection Heat Storage Unit. These are plate type intense collectors with built-in insulated tanks. The unit uses convection (movement of hot water upward) to move the water from heater to tank. Neither pumps or electricity are used. It is more efficient than an ICS as the intense collector heats a small amount of water that is constantly rising to the tank. It can be used in areas with less sunshine than the ICS. A passive open loop system Direct ('open loop') compact systems, if made of metals are not suitable for cold climates. At night the remaining water can freeze and damage the panels, and the storage tank is exposed to the outdoor temperatures that will cause excessive heat losses on cold days. Some compact systems have a primary circuit. The primary circuit includes the collectors and the external part of the tank. Instead of water, a non-toxic antifreeze is used. When this liquid is heated up, it flows to the external part of the tank and transfers the heat to the water placed inside. ('closed loop'). Open loop (direct) systems have the disadvantage that during the night-time, where the temperature of the solar panel starts to drop below that of the water tank, the system starts working in reverse heating the water in the panel and cooling the water inside the tank. This problem is least noticeable in closed loop system using a heat exchanger as only the water in the heat exchanger and not the whole tank is affected by it. Zhuhai Tianke Energy Saving Equipment Manufacture Co., Ltd. managed to solve this problem using a patented design in their solar water heating systems heat exchanger which forces the flow of the water in the in the heat exchangers inlet pipe in an upward flow, thus restricting cold water flowing down to the panel.The force of the flow is made through a driver inside the heat exchanger (jacket). The jacket and the driver part is made of the same heat conducting material therefore sharing the same temperature on same levels of the heat exchanger. Pumped systems (active systems) :- The solar water heating system is pumped and controlled determines whether it is a zero carbon or a low carbon system. Low carbon systems principally use electricity to circulate the fluid through the collector. The use of electricity typically How reduces the carbon savings of a system by 10% to 20%. Conventional low carbon system designs use a mains powered circulation pump whenever the hot water tank is positioned below the solar panels. Most systems in northern Europe are of this type. The storage tank is placed inside the building, and thus requires a controller that measures when the water is hotter in the panels than in the tank. The system also requires a pump for transferring the fluid between the parts.[32] The electronic controllers used by some systems permit a wide range of functionality such as measurement of the energy produced; more sophisticated safety functions; thermostatic and time-clock control of auxiliary heat, hot water circulation loops, or others; display or transfer of error messages or alarms; remote display panels; and remote or local datalogging. Newer zero carbon solar water heating systems are powered by solar electric (photovoltaic or PV) pumps. These typically use a 5-20W PV panel which faces in the same direction as the main solar heating panel and a small, low power diaphragm pump or centrifugal pump to circulate the water. |
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