Page 104 - GRIHA Manual Volume III - Introduction to National Rating System
P. 104
Renewable energy application 97
CRIteRIon 19
RenewAble-eneRGy
bAsed Hot wAteR
systeM
Introduction
Hot water is required in buildings for various purposes like washing, bathing, and cooking.
Conventionally, fossil fuels like natural gas, liquefied petroleum gas, oil, and coal are used as energy
sources for heating water. They can be used directly or in the form of electricity, though, either
way, combustion of fossil fuels results in greenhouse gas emissions and increase in environmental
pollution. However, use of renewable energy-based systems for heating water provides a clean and
green solution to this problem. Use of solar energy for water heating applications is one of the most
commercialized options. Solar thermal technologies have achieved high levels of technological
maturity worldwide and are economically feasible as well.
Solution
Solar water heaters (SWH)
Sun is an unlimited source of energy. India, being a tropical country, is blessed with plenty of
sunshine. The average daily solar radiation varies between 4 kWh/m and 7 kWh/m for different
2
2
parts of the country. There are, on an average, 250–300 clear sunny days in a year. Thus, the country
receives about 5000 trillion kWh of solar energy in a year. The annual global radiation varies from
1600 kWh/m to 220 kW/m (Arjunan, Aybar, and Nedunchezhian 2009).
2
2
Solar water heater is a device that collects solar radiation and heats water in the process. A typical
solar water heater comprises solar collectors for collection of incident solar radiation, insulated hot
water tanks for storage of hot water, plumbing, controls, and instrumentation. The amount of hot
water produced from a solar water heater depends on the design and climatic parameters such as
solar radiation, ambient temperature, and prevailing wind speed.
Components of typical solar water heating system
Solar collectors
Flat-plate solar collector: A liquid flat-plate solar collector (FPC) is a widely used solar energy
o
collection device for applications that require heat at temperatures below 80 C. A typical liquid FPC
consists of a selectively black coated absorber plate of high thermal conductivity (such as copper
or aluminium), one or more transparent covers, thermal insulation, heat removal system, and outer
casing. The transparent cover reduces the heat losses from the absorber plate to the surroundings.
For temperatures higher than 80 C, two glass covers may also be used. The heat collected by the
o
absorber plate is extracted by circulating a working fluid through the riser tubes attached to the
absorber plate, which are further connected to a larger pipe called header at both ends. The working
CRIteRIon 19
RenewAble-eneRGy
bAsed Hot wAteR
systeM
Introduction
Hot water is required in buildings for various purposes like washing, bathing, and cooking.
Conventionally, fossil fuels like natural gas, liquefied petroleum gas, oil, and coal are used as energy
sources for heating water. They can be used directly or in the form of electricity, though, either
way, combustion of fossil fuels results in greenhouse gas emissions and increase in environmental
pollution. However, use of renewable energy-based systems for heating water provides a clean and
green solution to this problem. Use of solar energy for water heating applications is one of the most
commercialized options. Solar thermal technologies have achieved high levels of technological
maturity worldwide and are economically feasible as well.
Solution
Solar water heaters (SWH)
Sun is an unlimited source of energy. India, being a tropical country, is blessed with plenty of
sunshine. The average daily solar radiation varies between 4 kWh/m and 7 kWh/m for different
2
2
parts of the country. There are, on an average, 250–300 clear sunny days in a year. Thus, the country
receives about 5000 trillion kWh of solar energy in a year. The annual global radiation varies from
1600 kWh/m to 220 kW/m (Arjunan, Aybar, and Nedunchezhian 2009).
2
2
Solar water heater is a device that collects solar radiation and heats water in the process. A typical
solar water heater comprises solar collectors for collection of incident solar radiation, insulated hot
water tanks for storage of hot water, plumbing, controls, and instrumentation. The amount of hot
water produced from a solar water heater depends on the design and climatic parameters such as
solar radiation, ambient temperature, and prevailing wind speed.
Components of typical solar water heating system
Solar collectors
Flat-plate solar collector: A liquid flat-plate solar collector (FPC) is a widely used solar energy
o
collection device for applications that require heat at temperatures below 80 C. A typical liquid FPC
consists of a selectively black coated absorber plate of high thermal conductivity (such as copper
or aluminium), one or more transparent covers, thermal insulation, heat removal system, and outer
casing. The transparent cover reduces the heat losses from the absorber plate to the surroundings.
For temperatures higher than 80 C, two glass covers may also be used. The heat collected by the
o
absorber plate is extracted by circulating a working fluid through the riser tubes attached to the
absorber plate, which are further connected to a larger pipe called header at both ends. The working
