Design and Performance Evaluation of Low Cost Domestic Solar Water Heating System in Kenya
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Date
2025-11
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Kenyatta University
Abstract
Kenya’s energy consumption is dominated by biomass, with an estimated 75% of
households relying on firewood and charcoal for cooking, heating, and lighting. This
dependency accelerates deforestation, contributes to indoor air pollution, and poses severe
health risks. Yet, Kenya’s equatorial location provides abundant solar energy, averaging 4–6
kWh/m² per day, making solar water heating (SWH) a sustainable and eco-friendly
alternative. Despite this potential, SWH technology adoption has been limited due to high
installation costs, dependence on imported copper collectors, and inadequate local
manufacturing capacity.
This study focused on the design, construction, and evaluation of low-cost flat plate solar
water heating systems (FPSWHS) using locally available materials, tested under real
Kenyan climatic conditions. The experiments were carried out at Kenyatta University in
Kiambu County (1°10'50.0"S, 36°55'41.0"E) between March and May 2015, a period
marked by alternating sunny and cloudy weather patterns. Two prototype systems were
developed: System A, incorporating an aluminum absorber plate, and System B, utilizing
galvanized steel. Both were designed and fabricated locally at the Kenya Industrial Research
and Development Institute (KIRDI). A commercially manufactured copper-based collector
imported from China (System C) was used as the control. System sizing was based on the
estimated hot water demand of a typical five-member household, with each person requiring
approximately 20 liters of water heated to 50°C per day. Using local solar irradiance data
(approximately 800 W/m²), estimated daily water consumption, and standard thermal design
equations, each system was optimized to efficiently meet domestic hot water needs
The experimental setup comprised three flat plate solar water heating systems, each with a
collector area of 2 m², tested simultaneously under actual field conditions. Solar radiation
was measured using a pyranometer, while outlet water temperatures were recorded hourly
using digital thermometers positioned at the outlets of each system. All three systems
successfully heated water above the 50°C threshold recommended by the World Health
Organization (WHO) for safe domestic use. The highest outlet temperatures recorded were
78.7°C for the copper collector, 74.1°C for aluminum, and 69.4°C for galvanized steel, with
corresponding mean outlet temperatures of 63.5°C, 61.2°C, and 57.3°C, respectively.
Thermal efficiencies were calculated as 34.0% for copper, 32.8% for aluminum, and 28.8%
for galvanized steel. Although the galvanized steel system demonstrated the lowest
efficiency, it was the most economical, costing Ksh 45,996.80 (USD 353.82), which is
approximately 20% less than the aluminum system at Ksh 54,160 (USD 416.61) and
significantly cheaper than the copper system at Ksh 68,664 (USD 528.18). Additionally, the
aluminum collector showed a payback period of 24 months, indicating a favorable balance
between performance and investment.
The findings demonstrate that low-cost, locally manufactured solar water heating systems—
particularly those constructed with galvanized steel—offer an affordable, sustainable, and
effective solution for meeting domestic hot water needs in Kenya. The widespread adoption
of such systems has the potential to significantly reduce reliance on biomass fuels, thereby
mitigating environmental degradation and deforestation. Additionally, improved access to
clean hot water can enhance public health outcomes by reducing waterborne diseases and
improving hygiene. These benefits align with the objectives of Kenya’s Vision 2030 and
contribute to the achievement of global sustainability goals.
Description
A Thesis Submitted in Partial Fulfilment of the Requirements for the Award of Degree of Master of Science (Renewable Energy) in the School of Engineering and Technology of Kenyatta University, September, 2025
Supervisor;
1.Mary Makokha
2.Moses Makayoto