Types of Solar Thermal Systems

There are quite a few different types of Solar Thermal systems available. Now with all of these different types of systems how do you figure out what systems is best for your heating needs. In some cases the climate can play a big factor in deciding what systems are appropriate. Lets cover the different types of systems first.


Non-Glazed Collectors:

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These types of collectors are typically used in pool heating applications. It is fairly easy to tell these types of collectors apart from others. They are typically made out of black plastic like material. They can come in many shapes and sizes. These types of panels are the least expensive and can have a 3 to 5 year payback if replacing a natural gas heater. Non-glazed collectors can not be used during freezing conditions.



Glazed Flat Plate Collectors:

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When talking about solar thermal, Flat Plat Collectors are what people tend to be most familiar with. A glazed flat plate collector consists of a shallow rectangular box with
transparent glass covering a flat black plate. The black plate is attached to a series of parallel tubes or one serpentine tube through which air, water, or other heat transfer fluids pass. As the sunlight passes through the collector’s glazing, it strikes an absorbing material. This material converts the sunlight into heat, and the glazing prevents the heat from escaping. These systems can be used for heating the domestic hot water, hot tub's, radiant floors, etc...



Glazed Evacuated Tube Collectors:

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An evacuated tube collector consists of parallel rows of glass tubes connected to a header pipe. Each tube has the air removed from it to eliminate heat loss through convection and radiation. The evacuated tubes are used in the same type of applications as flat plate collectors; however, they can achieve higher temperatures and are well-suited to commercial and industrial heating applications. They tend to be more efficient in cloudy climates and in low ambient temperatures due to the insulating quality of the vacuum. There are two types of evacuated tube systems, direct flow and heat pipe evacuated tubes.

Direct Flow: These consist of a group of glass tubes inside each of which is a flat or curved aluminum fin attached to a metal (usually copper) or glass absorber pipe. The fin is covered with a selective coating that absorbs solar radiation well but inhibits radiative heat loss. The heat transfer fluid is water and circulates through the pipes, one for inlet fluid and the other for outlet fluid. Very similar to how flat plate collectors operate.

Heat Pipe: These consist of a metal (copper) heat pipe, to which is attached a black copper absorber plate, inside a vacuum-sealed solar tube. The heat pipe is hollow and the space inside, like that of the solar tube, is evacuated. The reason for evacuating the heat pipe, however, is not insulation but to promote a change of state of the liquid it contains. Inside the heat pipe is a small quantity of liquid, such as alcohol or purified water plus special additives. The vacuum enables the liquid to boil (i.e. turn from liquid to vapor) at a much lower temperature than it would at normal atmospheric pressure. When solar radiation falls the surface of the absorber, the liquid within the heat tube quickly turns to hot vapor rises to the top of the pipe. Water, or glycol, flows through a manifold and picks up the heat, while the fluid in the heat pipe condenses and flows back down the tube for the process to be repeated.

Concentrating Solar Power Collectors:

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Unlike other solar thermal systems these systems are designed to produce power. Electricity generation is their primary purpose but depending upon the application they can provide both heat and power. Concentrating solar power use mirrors to reflect and concentrate sunlight onto receivers that collect the solar energy and convert it to heat. This thermal energy can then be used to produce electricity via a steam turbine or heat engine driving a generator. Smaller CSP systems can be located directly where the power is needed. Single dish/engine systems can produce 3 to 25 kilowatts of power and are well suited for such

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distributed applications. Larger, utility-scale CSP applications provide hundreds of megawatts of electricity for the power grid.

Solar thermal market grows 51.4% in the European Union

Solar thermal market grows 51.4% in the European Union

The European Union’s solar thermal market has clearly exceeded forecasts with 51.4% growth in 2008, equivalent to approximately 3,238.5 MWth. According to data presented in the latest EurObserv'ER solar thermal barometer, 20,000 MWth of solar thermal capacity was in service in the European Union at the end of 2008. Germany is outright leader, followed by Austria and Greece.

Germany really made the biggest difference doubling the amount of collectors installed in 2007. Whereas individual household installations are the major form of solar thermal application, the multi-occupancy market is starting to expand primarily providing hot water heating requirements of apartment blocks, service industry buildings, hotels, sportsfacilities and housing estates (grouped individual dwellings), and often offer combined heating and cooling systems. The political will to develop this type of application has a strong influence on national market penetration figures. In Austria, the collective share was put at 18% in 2008 (residential blocks: 11%; hotels and leisure amenities: 4%; and industry: 3%), while in Spain, the market is put at about 21.5%, or 100 000 m2. In mainland France, the figure is 18.2%. Market penetration is higher in Northern Europe – 55.2% of the Swedish market and 42% of the Danish market, because of the development of solar thermal in sports facilities (especially pools). The other European countries that have produced statistics on the collective market for 2008 are Poland (30.8%), the Czech Republic (11.1%), Cyprus (6.3%) and the Netherlands (4.7%).

On the basis of the ministry figures that follow, EurObserv’ER estimates the number of jobs generated by the solar thermal sector at over 50 000. As for sales, they should pass the 3 billion euro mark in 2008. The sector has very high potential for employment. ESTIF (European Solar thermal Federation) reckons that by 2020 the sector could be employing over 450 000 full-time staff.

The European market has firm foundations, aided by the implementation of national statutory frameworks (such as thermal regulations for buildings) and various incentive systems. The sector has considerable scope for expansion. According to a forthcoming study by ESTIF, solar thermal could cover over 10% of the additional renewable energy production required to achieve the European Union’s 20% goal by 2020.

Why Solar

The concept of using sun as an energy source is not new; even during ancient times the Greeks, the Chinese and the Native Americans were using the sun to warm their homes and keep them disease free.

So the question should be why not solar.

With all the energy that the sun is sending our way it wouldn't take much to satisfy our power needs through solar. I know it will take time but the technology is already there and all we really need is for our governments (and people) to start going forward on solar projects.

Jack Steinberger, the 1968 Nobel Prize winner in physics and director of CERN's particle-physics laboratory, spoke at a conference of Nobel laureates at the 350-year-old Royal Society in London last week.

His conclusion: "Wind is not the future," according to the London Times.

Steinberger says that solar energy is the future.

Historical resources in the energy-hungry world are being depleted, he said, predicting that fossil fuels, coal, and oil will be gone in 60 years. But the solution, he asserted, is not wind power.

The reason? Wind power still requires backup power when the wind isn't blowing, and that decreases its contribution to emissions reductions.

On the other hand, solar thermal power--where collectors concentrate sunlight using mirrors and lenses to produce electric power and heat--is already economical and can handle the storage problem, he said. The heat produced can be stored, enabling solar thermal plants to produce electricity during hours without sunlight.

We should keep in mind though that we should not forget about wind, one solution is not necessarily the right one for the whole world. Given the technology at the moment though all governments should really start looking into and supporting these solar thermal plants. For home owners solar thermal makes sense being close to if not the most affordable (for green energy produced) of the alternative energy market.

Solar Thermal: This is an excerpt from the Solar BC website.

Solar water heating typically offsets fossil fuel combustion, reducing greenhouse gas emissions and other pollutants. Systems can help reduce peak loads, thereby postponing or preventing the need for additional baseload energy generation and distribution infrastructure, such as new hydroelectric dams, coal-fired power generation stations, and underwater electrical cables.

Over its lifetime, a solar hot water system easily pays for itself and further provides proofing against a trend of rising energy costs. According to the British Columbia Utility Commission, natural gas prices have increased an average of 12% per year since 1998. With gas prices on the rise, using a solar hot water system will save you even more in the future.

Solar water heating systems fit well in the built environment and add little to our ecological footprint. Collectors are usually installed on rooftops, occupying otherwise unused space. Most equipment is made of locally available and recyclable materials: glass, plastic, copper, aluminium, wood, and steel. The full lifecycle impact is small, considering the 20+ years of service that a solar hot water system will give, producing zero-emission energy.