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There are a large
number of applications in which solar energy can be utilized directly
by exploiting its heat characteristics. Such technologies are
comparatively simple, relatively low cost and easy to adopt. The
applications include off and on grid power generation, cooking, heating
and cooling of buildings, generation of high temperature steam, heating
water for domestic and industrial applications, and drying agricultural
products under controlled temperatures. A brief description of these
applications in Solar Thermal Power
Generation (solar
Thermal world Installation upto 2011) SOLAR
THERMAL power
uses direct sunlight, called ‘beam radiation’ or Direct Normal
Irradiation (DNI). This is the sunlight that is not deviated by clouds,
fumes or dust in the atmosphere and which reaches the Earth’s surface
in parallel beams for concentration. Suitable
sites are those that get a lot of this direct sun – at least 2,000
kilowatt hours (kWh) of sunlight radiation per square meter annually.
The best sites receive more than 2,800 kWh/m2 a year. Typical regions
for Concentrated Solar Power (CSP) are those without large amounts of
atmospheric humidity, dust and fumes. They include steppes, bush,
savannas, semi-deserts and true deserts, ideally located within less
than 40 degrees of latitude north or south. The most
promising areas of the world include the south-western United States,
Central and South America, North and Southern Africa, the Mediterranean
countries of Europe, the Near and Middle East, Iran and the desert
plains of India, Pakistan, the former Soviet Union, China and
Australia. In these regions, 1 sq km of land is enough to generate as
much as 100-130 gigawatt hours (GWh) of solar electricity a year using
solar thermal technology. This is the same as the power produced by a
50 MW conventional coal or gas-fired mid-load power plant. Over the
total life cycle of a solar thermal power system, its output would be
equivalent to the energy contained in more than 5 million barrels of
oil. Like
conventional power plants, CSP plants need cooling at the so-called
“cold” end of the steam turbine cycles. This can be achieved through
evaporative (wet) cooling where water is available or through dry
cooling (with air) – both are the conventional technologies. Dry
cooling requires higher investment and eventually leads to 5 – 10%
higher cost compared to wet cooling. There is
another options which is Hybrid cooling. Hybrid cooling can optimize
performance for site conditions and these are under further
development. However, the huge solar power potential in these areas by
far exceeds local demand. So, solar electricity can be exported to
regions with a high demand for power but with less solar resource. If the
sun-belt countries harvest their natural energy in this way, they would
be making a big contribution to protecting the global climate. Certain
country such as How it
works – the technologies A range
of technologies can be used to concentrate and collect sunlight and to
turn it into medium to high temperature heat. This heat is then used to
create electricity in a conventional way, for example, using a steam or
gas turbine or a Solar
heat collected during the day can also be stored in liquid or solid
media such as molten salts, ceramics; concrete or phase-changing salt
mixtures. At night, it can be extracted from the storage medium to keep
the turbine running. Solar
thermal power plants with solar-only generation work well to supply the
summer CSP
plants produce electricity in a similar way to conventional power
stations – using steam to drive a turbine. The difference is that their
energy comes from solar radiation converted to high-temperature steam
or gas. To harness the solar thermal energy four main elements are
required: a concentrator, a receiver, some form of transport media or
storage, and power conversion. Many
different types of systems are possible, including combinations with
other renewable and non-renewable technologies. So far, plants with
both solar output and some fossil fuel co-firing have been favored,
particularly in landmark developments in the US and North Africa.
Hybrids plants help produce a reliable peak-load supply, even on less
sunny days. Experts
opinioned that concentrated solar plants are the most suitable and
viable solution to Solar
water heater (Concept
Clearance Paper of solar water heaters) Solar water heating
technology is quite mature but its use in Solar
dryer (Detail attached
in the brochure) Solar energy can be
utilized very effectively in drying agriculture products using solar
dryers, and good quality products can be obtained at much less cost due
to savings in cost of electricity or other heating fuels that would
have been used otherwise for the same purpose. Due to the lack of
logistics and basic infrastructure in the northern mountainous regions
of Gilgit and Sakardu etc tons of fruit like apricots go waste every
year. Solar dryers are now being used to dry large quantities of such
fruit, which are transported and sold them later in the urban market,
resulting in a positive effect on the economy of this area. Solar
dryers could be equally effectively used in the provinces of Recent achievement of
PCRET in solar Drying. Several models of solar
dryers have been developed by this council and are being disseminated. Ø
In Public Sector
Development Programme, Govt of Pakistan PCRET designed developed and
installed 10 unglazed collector type hybrid (Solar + Biomass) dryer
having 500 kg capacities for drying of dates in Punjab, Khyber
Pakhtoonkhwa. Ø
Designed solar dryer
for Pakistan Tobacco Board for Curing of Tobacco. Ø
Designed 500 kg
capacity solar tunnel dryer for drying of fruits and vegetables for
Govt of Sindh in this project Sindh Govt disseminate 80 solar dryers of
500 kg each in Sindh.
The unavailability of
drinkable water in large parts of Balochistan, Sindh and southern Solar
cooker A number of public
sector organizations have worked in the past and are still working on
the development of low cost and efficient designs of both box and
concentrator type solar cookers. Non-governmental organizations are
also active in this field and have supplied a number of such cookers to
rural areas. The Pakistan Council for Renewable Energy Technologies
(PCRET), which is later described in this paper, routinely organizes
training workshops on the use and maintenance of such devices. The
number of solar cookers in use in Solar cookers come in two types: box types that are more suitable for baking the food, and concentrated (parabolic) type that works at high temperatures. Foods prepared in solar ovens keep their natural flavor and taste and retain their vitamin content. Less oil is required for cooking in the solar oven, therefore, solar oven cooked food is good for weight conscious people. All Pakistani dishes
including prathas and chapatti can be prepared on concentrated type
cooker in the same time interval as taken by a conventional single
stove gas cooker. The method of cooking is also similar to that of
conventional cooker. The cooker emits no harmful smoke to harm eyes and
lungs of the cook. The cooking can be done on this cooker from |