62
B. S. Mukesh et al.
thermocouples are attached on to the receiver and the temperature is recorded using
NI DAQ system. The theoretical geometric concentration ratio predicted is 115 but
from the experiment a flux concentration ratio 94 is measured.
5.1 Introduction
Solar energy is a promising renewable source to meet the growing energy demand.
From the direct normal irradiance (DNI) map of India the abundance of solar radiation in Rajasthan, Gujarat, and Ladakh is obvious with an availability of more
than 5.5 kWh/m
2
/day NREL (2019). This energy can be harnessed for solar water
heating systems to provide hot water for both domestic and industrial sectors which
will reduce the electrical energy consumption. The solar water heater has many advantages, such as negligible global warming potential, lower payback period, ease
of manufacturing, and less maintenance Singh et al. (2016).
A large variety of solar water heater designs exist each with its own set of advantages and disadvantages. Flat plate solar water heaters consist of pipes welded
onto a metal plate collector, which is placed inside a rectangular case covered by
a glass with efficiency as high as 44% Ayompe and Duffy (2013a). Sae-Jung et al.
(2015) conducted experiments on a thermos-syphon based solar water heater, which
resulted in enhanced efficiency of 56%. Evacuated tube collectors consist of glass
vacuum-sealed metal absorber tube. Ayompe and Duffy (2013b) studied the thermal
performance of solar water heating system with evacuated heat-pipe tubular collector
and achieved efficiency of 62%. In general, evacuated tube collectors have higher
efficiency in comparison to flat-plate collectors. Diego-Ayala and Carrillo (2016)
compared performance of flat-plate water heating systems with thermos-syphon
and forced flow. They reported higher efficiency with forced flow in comparison
to thermos-syphon based system. Kakaza and Folly (2015) compared the alternative
energy sources to be provided for a particular demand. Results revealed that heat
pump based solar water heaters have short payback period even though the initial
investment is high. Papadimitratos et al. (2016) developed a new design by integrating evacuated tube solar collectors with phase change material (PCM) based thermal
energy storage. Here, heat pipe is immersed inside the phase change material, where
heat is effectively accumulated and stored for an extended period of time. Evacuated tube collectors also have better thermal insulation in comparison to a flat-plate
collector, which enhances the overall efficiency. The efficiency of the Dual-PCM
solar water heater system has increased 26% compared with standard system. Xue
(2016) reported experimental investigation of a domestic solar water heater coupled
with phase change material based energy storage. Robles et al. (2014) conducted
experiments on a non-evacuated aluminium based mini channel solar water heater,
which resulted in an average increase in thermal efficiency of 13% compare to flat
plate collector. Deng et al. (2015) presented a novel flat plate solar water heater using
micro heat pipe array sprayed with solar selective coating and arranged closely as
the absorber of collector.The experiment was conducted on a 2 m
2 flat plate collector
B. S. Mukesh et al.
thermocouples are attached on to the receiver and the temperature is recorded using
NI DAQ system. The theoretical geometric concentration ratio predicted is 115 but
from the experiment a flux concentration ratio 94 is measured.
5.1 Introduction
Solar energy is a promising renewable source to meet the growing energy demand.
From the direct normal irradiance (DNI) map of India the abundance of solar radiation in Rajasthan, Gujarat, and Ladakh is obvious with an availability of more
than 5.5 kWh/m
2
/day NREL (2019). This energy can be harnessed for solar water
heating systems to provide hot water for both domestic and industrial sectors which
will reduce the electrical energy consumption. The solar water heater has many advantages, such as negligible global warming potential, lower payback period, ease
of manufacturing, and less maintenance Singh et al. (2016).
A large variety of solar water heater designs exist each with its own set of advantages and disadvantages. Flat plate solar water heaters consist of pipes welded
onto a metal plate collector, which is placed inside a rectangular case covered by
a glass with efficiency as high as 44% Ayompe and Duffy (2013a). Sae-Jung et al.
(2015) conducted experiments on a thermos-syphon based solar water heater, which
resulted in enhanced efficiency of 56%. Evacuated tube collectors consist of glass
vacuum-sealed metal absorber tube. Ayompe and Duffy (2013b) studied the thermal
performance of solar water heating system with evacuated heat-pipe tubular collector
and achieved efficiency of 62%. In general, evacuated tube collectors have higher
efficiency in comparison to flat-plate collectors. Diego-Ayala and Carrillo (2016)
compared performance of flat-plate water heating systems with thermos-syphon
and forced flow. They reported higher efficiency with forced flow in comparison
to thermos-syphon based system. Kakaza and Folly (2015) compared the alternative
energy sources to be provided for a particular demand. Results revealed that heat
pump based solar water heaters have short payback period even though the initial
investment is high. Papadimitratos et al. (2016) developed a new design by integrating evacuated tube solar collectors with phase change material (PCM) based thermal
energy storage. Here, heat pipe is immersed inside the phase change material, where
heat is effectively accumulated and stored for an extended period of time. Evacuated tube collectors also have better thermal insulation in comparison to a flat-plate
collector, which enhances the overall efficiency. The efficiency of the Dual-PCM
solar water heater system has increased 26% compared with standard system. Xue
(2016) reported experimental investigation of a domestic solar water heater coupled
with phase change material based energy storage. Robles et al. (2014) conducted
experiments on a non-evacuated aluminium based mini channel solar water heater,
which resulted in an average increase in thermal efficiency of 13% compare to flat
plate collector. Deng et al. (2015) presented a novel flat plate solar water heater using
micro heat pipe array sprayed with solar selective coating and arranged closely as
the absorber of collector.The experiment was conducted on a 2 m
2 flat plate collector