Page 48 - Engineering in Kenya Mag

The Potential Application of Solar Thermal Powered Adsorption Chillers for Cooling Houses in Nairobi
KINTRODUCTION those occupying these houses. This was based on literature review of the
study investigated the potential of using adsorption chillers in place of the conventional air conditioning systems. Because adsorption chillers need hot water to run, the possibility of using solar thermal heating systems to meet this requirement is investigated. Therefore, the paper first sets out to review the housing situation in Nairobi county and the status of electricity consumption, especially, on meeting the cooling load demand. Next, a model is developed to calculate, based on the climatic conditions in Nairobi, the solar thermal heating potential for per square meter for Flat Plate Collector (FPC) solar thermal heaters, the cooling load for standard 3-bedroom house is then evaluated, assuming a Coefficient of Performance (C.O.P) of 0.3. Finally, the model determined the size of FPC’s need to heat the water needed to meet the cooling demand and the practicability of this system is evaluated.
Approach
The study developed a solar thermal run adsorption cooling system for a three-bedroom residential housing unit. The performance metric adopted by the study was a C.O.P of 0.3 that
ENYA is a tropical country in East Africa and enjoys relatively good climate throughout the year. According
to the 2019 Kenya Population and Housing Census, Kenya had a total population of approximately 47.5 million. Notably, Nairobi county had a population of approximately 4.4 million people, and with a land area of 703.9 square kilometers, this translates to 6,247 people per square kilometer. This population density was by far the highest among the counties, which only serves to increase competition for the resources available in the county. To address the perennial challenge of scarce housing facilities in the country, the Government of Kenya under the ‘Big 4 Agenda’, has set in motion a rigorous plan to construct a projected 500,000 units by 2022. Markedly, the capital county, Nairobi, with its high population density, is set to be the biggest beneficiary of this plan with its high population density.
To improve the living conditions in the constructed houses, one of the factors that needs to be considered is air conditioning. Of particular importance is the ability to cool these houses during the hot seasons to make the spaces more habitable to
performance of other systems. The methodology involved developing an Excel model to first, estimate the heat generated by location specific solar irradiance per square meter. The system then computed the average cooling capacity per square meter, followed by an evaluation of the cooling load of a three-bedroom residential house as case study. Finally, the model determines the size of the solar collector system needed to provide the cooling load and the practicability of the system is appraised.
The proposed system contains two beds, which operate intermittently to create a continuous cooling cycle. The choice of this system is based on its superior efficiency compared to a single bed adsorption system. The other components include the condenser, hot water tank, evaporator, solar heat energy collector, pipes, valves, and sensors. An illustration of the
The solar heat collector comprised of flat plate collectors. Essentially, the flow of working fluid would be:
l Flatplatesolarcorrectorgathers heat from the sun
l The heat is transferred to the hot water circulating through the solar
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Engineering in Kenya Magazine Issue 002