ponedjeljak, 21. veljače 2011.
CCRES - SOLAR DRY FACTS
CROATIAN CENTER OF RENEWABLE ENERGY SOURCES
SOLAR DRY FACTS
Concentrating solar power technologies 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.
Another solar generating technology uses photovoltaic cells (PV) to convert sunlight directly into electricity. PV cells are made of semiconductors, such as crystalline silicon or various thin-film materials. Photovoltaics can provide tiny amounts of power for watches, large amounts for the electric grid, and everything in between.
Solar Power can be used almost anywhere at a variety of scales
Low-temperature solar collectors also absorb the sun’s heat energy, but instead of making electricity, use the heat directly for hot water or space heating in homes, offices, and other buildings.
Even larger plants than exist today are proposed for construction in the coming years. Covering 4% of the world’s desert area with photovoltaics could supply the equivalent of all of the world’s electricity. The Gobi Desert alone could supply almost all of the world’s total electricity demand.
Photovoltaic Cells Convert Sunlight into Electricity
A photovoltaic cell, commonly called a solar cell or PV, is the technology used to convert solar energy directly into electrical power. A photovoltaic cell is a nonmechanical device usually made from silicon alloys.
How Photovoltaic Systems Operate
The photovoltaic cell is the basic building block of a photovoltaic system. Individual cells can vary in size from about 0.5 inches to about 4 inches across. However, one cell only produces 1 or 2 watts, which isn’t enough power for most applications.
To increase power output, cells are electrically connected into a packaged weather-tight module. Modules can be further connected to form an array. The term array refers to the entire generating plant, whether it is made up of one or several thousand modules. The number of modules connected together in an array depends on the amount of power output needed.
Weather Affects Photovoltaics
The performance of a photovoltaic array is dependent upon sunlight. Climate conditions (such as clouds or fog) have a significant effect on the amount of solar energy received by a photovoltaic array and, in turn, its performance. Most modern modules are about 10% efficient in converting sunlight. Further research is being conducted to raise this efficiency to 20%.
Commercial Applications of Photovoltaic Systems
The success of PV in outer space first generated commercial applications for this technology. The simplest photovoltaic systems power many of the small calculators and wrist watches used every day. More complicated systems provide electricity to pump water, power communications equipment, and even provide electricity to our homes.
Some advantages of photovoltaic systems are:
•Conversion from sunlight to electricity is direct, so that bulky mechanical generator systems are unnecessary.
•PV arrays can be installed quickly and in any size.
•The environmental impact is minimal, requiring no water for system cooling and generating no by-products.
Photovoltaic cells, like batteries, generate direct current (DC), which is generally used for small loads (electronic equipment). When DC from photovoltaic cells is used for commercial applications or sold to electric utilities using the electric grid, it must be converted to alternating current (AC) using inverters, solid state devices that convert DC power to AC.
Solar Thermal Collectors
Heating With the Sun’s Energy
Solar thermal (heat) energy is often used for heating water used in homes and swimming pools and for heating the insides of buildings (“space heating”). Solar space heating systems can be classified as passive or active.
Passive space heating is what happens to your car on a hot summer day. The sun’s rays heat up the inside of your car. In buildings, the air is circulated past a solar heat surface and through the building by convection (meaning that less dense warm air tends to rise while denser cool air moves downward). No mechanical equipment is needed for passive solar heating.
Active heating systems require a collector to absorb and collect solar radiation. Fans or pumps are used to circulate the heated air or heat absorbing fluid. Active systems often include some type of energy storage system.
Solar Collectors Are Either Nonconcentrating or Concentrating
Nonconcentrating collectors — The collector area (the area that intercepts the solar radiation) is the same as the absorber area (the area absorbing the radiation).Flat-plate collectors are the most common type of nonconcentrating collector and are used when temperatures below about 200°F are sufficient. They are often used for heating buildings.
There are many flat-plate collector designs but generally all consist of:
•A flat-plate absorber that intercepts and absorbs the solar energy
•A transparent cover(s) that allows solar energy to pass through but reduces heat loss from the absorber
•A heat-transport fluid (air or water) flowing through tubes to remove heat from the absorber, and a heat insulating backing
Concentrating collectors — The area intercepting the solar radiation is greater, sometimes hundreds of times greater, than the absorber area.
Solar Power Applications
Solar Electricity (PV)
Photovoltaic systems convert sunlight into electricity to power your home or business. PV is quickly becoming popular as a reliable, low-maintenance, clean, low-cost energy alternative. Solar electricity allows you to be as energy independent as you choose, while lowering your utility bills and carbon emissions. It’s particularly popular with our customers in Florida, Georgia and the Caribbean where there’s an abundance of free sunlight. Solar panels come in a variety of styles for mounting on the ground or on rooftops.
Solar Water Heaters
Our customers love their solar hot water systems. Solar thermal technology has been perfected over many decades to provide a greater abundance of hot water than possible with electric or gas heaters – all with the sun’s free energy. Because the initial investment is small and the monthly savings are large (reducing the average electric bill by 25%), solar water heaters provide a quick return on investment. A popular option for homes, offices and factories, solar water heaters offer low-cost, low-maintenance hot water year-round.
Solar Pool Heaters
Compared to gas or electric heaters, solar pool heaters offer the only affordable option for homeowners who want to enjoy their pools year-round. Pool owners throughout the Southeast and Caribbean swim comfortably ten months of the year, or more, with solar-heated water. Still greatly misunderstood, solar energy can easily heat your pool in the high 80s and low 90s – and yes, that’s how most of our customers like their pool water. Most homeowners simply can’t afford to maintain such temperatures using gas or electric heaters.
“Day-lighting” is a common term for harnessing natural light to illuminate internal spaces. By designing windows and other openings to work with reflective surfaces, we can bring in sunlight to maximize your visual comfort and reduce energy use. “Solar tubes” are a popular day-lighting product for both new construction and remodeled homes to dramatically brighten dim internal spaces. SunWorks also offers solar landscaping products for night-lighting in exterior spaces using free energy.
Solar Attic Fans
Proper attic ventilation is vital for reducing your heating/cooling costs and for releasing trapped moisture. Passive vents that rely on wind to circulate attic air have been a requirement in building codes for many years. Solar attic vents provide more effective results because they harness the sun’s free energy to assure constant air circulation with little maintenance.
Solar Power Benefits and Savings
Is it not time to start letting the sun work for you??
Under our climatic conditions (Europe) a properly installed solar hot water system should provide at least 80% of household’s hot water supply!! With ever increasing electricity and gas prices. This proves to be a huge a saving over the mid-term. Local authorities also have very attractive grant schemes in place. Depending on the area and the kind of installation, home owners can expect between thirty and forty percent of the total cost back.
Care needs to be taken before undertaking any project and it is very important to deal only with a company that is authorized to carry out the installation and the grant application on your behalf.
Ways You Save With Solar
•Lower your electric bill
•Reduce your carbon footprint
•Stabilize your utility costs
•Increase your property value
•Reduce utility power dependence
•Enjoy decades of free hot water
•Extend your swimming seasons
•Power your home pollution-free
•Maintain power during utility outages
•Decades of low maintenance energy
•Be as energy independent as you like
•Less use of fossil fuels and foreign oil
Although Solar energy is considered to be one of the cleanest and renewable sources of energy among the available sources but is has some environmental impacts too. Solar energy uses photovoltaic cells to produce solar power. However, manufacturing the photovoltaic cells to produces that energy requires silicon and produce some waste products. Inappropriate handling of these materials may lead to hazardous exposure to humans and the environment. Installing solar power plants may require large piece of land, which may impact existing ecosystems. Solar energy does not pollute the air when converted to electricity by solar panels. It is found in abundance and does not help in global warming.
Solar Power Calculations
You, too, can size your solar array, or solar panels, in just two easy steps!
To estimate the size of your solar array, you’ll need to know:
•The number of Watt-hours (Wh) you plan to produce in one day.
•The insolation value at your location.
A Watt-hour is a measure of energy. Identifying your Watt-hours goal is the most crucial part of accurately estimating how big a system–or we might say, how many Watts of solar panel generating capacity–you will need. If you plan to tie your solar array directly to the utility grid to offset your costs, start by looking at your electric utility bill for the kilowatt-hours (abbreviated “kWh”) you use in one month. Since your electricity usage probably changes throughout the year, you might want to calculate your average monthly usage from the historical information found on most bills these days. People often choose to offset a certain portion of their average electricity usage based on their budget.
We are trying to obtain the number of Watts, in solar panels, we need to produce a given amount of Watt-hours (or kWh) for our project in our location.
Take the number of Watt-hours (or kWh) you want to produce in one day and divide it by the insolation value, in hours. Example: 8 kWh / 4 hours = 2 kilowatts (kW)
Allow for the normal energy losses and inefficiencies in a solar electric system. Do this by increasing the number of Watts (or kilowatts) you found in Step 1 by 30%. Example: 2 kW x 1.3 = 2.6 kW
Now you know you can look for a 2.6 kW (or 2,600 Watt) system in order to produce, on average, 8 kWh per day (240 kWh per month) in our example location with its average of 4 hours of insolation. Expect an installed cost of approximately eg. 15 Euro per Watt; this system would cost about 39.000 Euro installed.
CROATIAN CENTER OF RENEWABLE ENERGY SOURCES ( CCRES )