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Tag Archives: Renewable

solar absorption chillersAir conditioning makes up bulk of the power usage, especially in tropical countries where the sun is shining almost throughout the year and the humidity levels are high. It makes a perfect sense to use solar heat to cool homes, business and factories. Many air-conditioning systems are commercially available using simple roof top PV solar panels to generate electric power to run an electric window air-conditioners. This system uses commercially available solar panels and window air-conditioners and uses solar power to generate electricity to run the compressor and the blower in the air-con unit. This system requires large storage battery to store adequate electricity to run your air-conditioners for specified period. Otherwise it requires a large area of solar panels to meet the demand. The efficiency of such systems can be improved using DC operated compressors and fans. However, renewable energy such as solar is still expensive to run air-conditioners because of high initial investment cost, though it may be economical in the long run as the cost of solar panels and accessories slowly come down over a time. Moreover such systems are limited to small air condition capacities.

solar chillers-typical apacitiessolar absorption chillerFor large air-conditioning requirements such as business and factories, we need a system that uses solar heat directly to air-condition the premises with higher efficiency and thermal storage capabilities. Designing such a system is not very difficult because most of the components necessary to install such systems are readily available. One can install an air-conditioning system based on 100% solar thermal heat with molten salt thermal storage. Alternatively, a hybrid system can be installed based on solar heat without a thermal storage but using   city gas supply. Many countries use gas for heating during winter seasons but do not use gas during summer. These countries can use a hybrid (solar-gas) system to air-condition their premises and avoid peak electric usage during summer seasons thereby avoiding electrical black-outs. The advantage with such system is they can also be used for heating the premises during winter season. With changing climate due to global warming many warm countries like India also experiences cold temperatures during winter season. For example New Delhi in India has experienced a sharp drop in temperature up to 15-20c during winter from earlier winters.

Solar cooling systems to date have used waste heat gas absorption chiller heaters, which utilize the waste heat from cogeneration systems (CGS) for the cold water. However, these chiller heaters with their established technologies are devices designed for the effective use stable CGS high-temperature waste heat, so they cannot accommodate the preferential use of solar heat when solar hot water temperatures suddenly change from large variations in the heat collector temperatures due to changes in the weather. The new solar absorption chiller heaters are now specially designed for the effective use of low-temperature solar heat to address this problem and improve the energy conservation effect from solar cooling system. Hot water at less than 90C can be used for such systems and typical chillers with their rated specification are shown in the figures.solar trough

The efficiency of the system can be vastly improved by using parabolic solar concentrators, up to 27 times higher than ordinary flat plate solar collectors resulting in conversion efficiency up to 85% in heating and cooling. By selecting a natural refrigerant such as R717 we can save the environment from ozone depletion. Such systems offer flexibility to use exhaust heat, natural gas along with solar thermal storage up to 220C (phase transition temperature).The system offers an attractive return on investment, electricity savings and Carbon pollution reduction. The system can be designed from 5TR up to 200TR refrigeration capacity for 100% solar and up to 1000TR for a solar-gas hybrid systems. The solar thermal system with molten salt storage is versatile in its application because the same system can be designed for heating or cooling or on-site power generation for continuous applications.

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The city of Athens hosted its oldest tradition of lighting the Olympic torch for the 2012 London Olympic Games on Thursday in Olympia. The torch was lit by solar power; using parabolic mirror to redirect the sun’s light to light the flame with purest natural light. The thermal energy of sun’s light can be powerful when focused to a point and it can reach a temperature as much as 600C.The parabolic trough with reflective mirror focuses the sunlight on the tube called ‘collectors’ in which a fluid with high boiling point is circulated. The hot fluid in turn is used to convert water into steam in boiler. The hot oil transfers its heat to the water in a heat exchanger and returns back to the parabolic trough. It is a closed circuit system. The hot oil at 390C generates steam at 370C at 100 bar pressure, which is used to run a HP steam turbine. The standard steam condensing cycle generates power similar to fossil fuel fired power plant. A 50 Mw Trough plant in Israel (Negev Desert) is already in operation.

The capacity of such plant can be easily expanded by adding modular parabolic troughs and collectors and the plant can be designed to meet  specific power demands. This is a straight forward method to generate base load power using standard steam cycle. The efficiency of such system will be 41% maxium.However recently few companies are trying use a combined cycle. This increase the solar to heat efficiency from 50.5% to 53.6%.This nominal 50Mw power plant generates  a total peak power of 57.10Mw using a solar collection area of 310,028m2 with annual solar to electrical efficiency at 16.3% using a water-cooled condenser in the steam cycle. The cost of energy works out to $0.23 to $ 0.25 /kwhrs.

By using a central solar collection tower (Heliostat) and bottoming with Rankin/Kalina cycle ,it is estimated that the total installed cost can be reduced by 10%.The system can be configured from 2Mw up to 100Mw using both trough and tower system. The system can be installed in any remote, arid locations using air condensers, where cooling water is a problem. The estimated annual specific energy cost is less than 6 cents/kwhrs, comparable to low-cost fossil energy but with zero pollution and with zero carbon emission.

Solar thermal is a potential clean energy of the future for many countries around the world with yearlong sunshine with good intensisty.The solar thermal energy can also be used in many process industries where thermal heating is required. Solar salt pans can use solar thermal energy very efficiently to cut their production cycle. The concentrated brine can be used as a circulation fluid in solar collectors and also be used to generate power using low heat technologies like Kalina cycle, because concentrated salt brine can store thermal heat.

Gemasolar power in Spain is a base load power station supplying power for 25,000 homes 24×7 using molten salt (60% KNO3+40% NaNO3) as a thermal storage medium instead of batteries. Nine plants were built in 1980 in Mojave Desert with a combined capacity of 354 Mws.

Other examples of solar base load power plants are Blythe solar with capacity of 968Mw at Riverside County, California and Ivanpah power station with capacity of 370 Mw capacities in US. Large scale solar base load plants are no longer a theory but a commercial reality.

Direct solar lighting is also being introduced using fiber optics. The sun light is collected at a central point and directed through fiber optics to various rooms inside the building supplying direct sun light. This saves not only electricity but also provides natural light to work places because human body requires a certain amount of UV light exposure. Solar energy is here to stay and offer various clean energy solutions in the future.

 

 

There are many ways to increase the energy efficiency of an existing system which also helps invariably to cut your carbon footprint. The inefficiencies breed pollution. Such inefficiencies can emanate from power generation methods or from power distribution methods. Energy cannot be stored but has to be used. That is one of the main reasons why the power companies look for large consumers and offer them the lowest tariff. Some industries like Caustic soda plants and Aluminum smelters, consume large power.

If you are using power from the grid then you can discuss with your service provider and check whether you can switch over to green power. The tariff may be slightly higher than a standard tariff but certainly helps you to reduce your carbon footprint. Some service providers show your carbon foot print by way a chart in their monthly energy bill. Most of the energy providers supply green power such as solar and wind as part of their energy mix to make sure that they don’t lose customers who may insist on green power.

You can check various power tariffs in your place such a peak tariff and off-peak tariffs and you will be surprised at the difference. The peak tariff is when everybody use power , normally 9am to 5pm.The usage of air-conditioners  during peak hours in  tropical countries is high They can use rooftop  solar panels with batteries and inverters because many counties in Asia do not have  feed-in tariff method by which you can export your surplus solar power to the grid. Moreover they do not have a choice in selecting a service provider because power generation and distribution are mostly runs by Governments or by very few service providers. The best method for such users is to store the solar energy in batteries and use them when they want. Even consumers who use grid power can store electricity during off-peak period using batteries and then use them during peak period using an inverter. This is an ideal solution for Asian countries where the power outage is frequent and unexpected.

The best method will be to use an Electrolyzer to generate Hydrogen using off-peak power and tape water and store them under pressure. You can generate your own electricity using small Fuel cell .This electricity can be a Direct current that can be readily connected to a host of Direct current operated appliances including your air-conditioners and refrigerators. If your electricity load is relatively high then you can integrate both solar panels and grid power in such a way that you can store enough electricity by way of Hydrogen or in a battery and use them during peak period. By this method you can be certain of an uninterrupted power supply and at the same time a reasonable power tariff. You can reduce your carbon foot print substantially   by utilizing solar power with Hydrogen storage.

You can choose energy-efficient appliances by looking at their star ratings.A star rating of 6 and above is considered very energy-efficient. You can choose LED bulbs for lighting and I would suggest using Direct current for LED bulbs directly from Fuel cell or battery and not from grid supply using an inverter. You can also check the type of refrigerants used in air conditioners and Refrigerators and their star ratings. If you have a roof top solar panel as part of electricity supply then I will recommend to use Direct current operated Air-conditioners and regfigerators.When you choose these appliances you can look for the type of motor, compressor and fans  used, because these are the main parts that use electricity. An energy-efficient motor and the type of compressor used are critical components in determining the capacity, airflow and noise levels. The energy ratings are based on these factors only.

You can save energy and cut your carbon footprint in every step of the way if you are keen to do it. The most important factor in achieving energy efficiency is an understanding of your contribution to the environment and the prudence with which you can achieve these goals.

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