Tag Archives: solar water heating

Solar Water Heating as an Energy Service – Part 1 – Technology Choices and Markets

Solar water heaters as a product have the potential to contribute considerably to energy demand reduction in developing countries. This exists both as a household-scale technology, and in industrial applications such as desalination in countries such as the UAE and Saudi Arabia, and industrial process heat in both developed and developing countries. A number of developing countries around the world, notably those in Sub-Saharan Africa, have had success in disseminating solar water heating products on a commercial basis, in addition to a number of large-scale government dissemination programs. Countries such as South Africa (with around 500,000 systems installed as of 2016) and China (which has over 85 million installed SWH units as of 2016) have developed a robust network of commercial installers and manufacturers of solar water heating units and parts, selling products on a market basis to households and businesses.

Solar water heater installed by ESKOM, South Africa. Image: gmourits, Flickr, via http://inhabitat.com/eskom-installs-solar-powered-heaters-on-south-african-roofs/


There are a number of opportunities in developing country markets to develop a solar water heating sector. A number of developing countries, particularly those in Sub-Saharan Africa, have high levels of insolation (sunlight kWh/m2/day), and a consistent demand across income segments of the population for water heating. Industrial process heat is another sector where solar water heating could have an impact, as is institutional process heat, for example heat exchangers for hospital refrigeration, and hot water for use in health centres and schools.

Entrepreneurs and companies looking to enter the solar water heating market space need to consider a number of questions before starting their operations. Firstly, an appropriate technology choice is essential for succeeding in the SWH market, perhaps more so than many other renewable energy technologies. Deciding which consumer segment or income bracket to target informs the technology decision somewhat, but thorough research needs to be done on what the market and consumers can afford before deciding on a technology. Main technology streams for SWH include flat-plate solar collectors, and evacuated tube solar collectors. Both work on similar principles, heating water that passes through the collector, either through capillary action or through the use of an electric pump. Flat-plate collectors can be slightly less efficient than evacuated tube designs due to heat loss through convection, however they are also less expensive and simpler to produce. Evacuated tube designs are generally more efficient at heating water, but are also more expensive to compensate for the increased complexity in manufacture.

Flat-plate solar collector installed on a house in the United Kingdom. Image: uk.solarcontact.com

Flat-plate solar collector efficiency vs evacuated tube efficiency at various temperature ranges for a typical North American location. Source: https://blog.heatspring.com/solar-thermal-flat-plate-or-evacuated-tube-collectors/


When designing a new solar water heating business or intervention, therefore, it is important to consider which variant on the technology is to be used, and at what scale (household, institutional, industrial etc.), in order to plan dissemination based on affordability for the consumer. The next blog in this series will investigate business and financing models that can assist in improving the sustainability and replicability of solar water heating energy service companies.

– Daniel Kerr, UCL Energy Institute


Clean Technica (2015) World’s Largest Solar Powered, Jellyfish-Fightin’ Desalination Plant To Be Built in Saudi Arabia. Available at: https://cleantechnica.com/2015/01/22/worlds-largest-solar-powered-desalination-plant-under-way/

Urban, Geall & Wang (2016) Solar PV and solar water heaters in China: Different pathways to low carbon energy. Renewable and Sustainable Energy Reviews, Vol. 64, pp. 531 – 542

EE Publishers (2016) Solar water heater rollout programme gains momentum. Available at: http://www.ee.co.za/article/solar-water-heater-rollout-programme-gains-momentum.html


What Could The Energy Transition Be for Thermal Energy Services in the Global South – Part 2

Following our previous post on cooking, this post will investigate space and water heating/space cooling needs.

Space and water heating/space cooling

Heating can be an important source of energy consumption in a number of developing countries located far from the Tropics. This function is often associated with cooking, where a central heating point is used both to cook meals and heat the house. Bio-digesters in countries like China, India or Nepal have been able to provide heat on top of cooking.

Another energy service which is more widely used – even if often not considered as a priority – is domestic hot water which can be provided with a solar water heater. South Africa has some very large programmes of dissemination of solar water heaters, notably in townships. Half of the population of Barbados has a solar water heater. Solar water heaters are a mature technology, which can be easily manufactured locally and relatively cheaply, most of the time sold on a cash basis or with a consumer credit.

david monniaux 2005 swh

Solar water heater used in the Cirque de MafateRéunion. “Solar heater dsc00632”. Licensed under CC BY-SA 3.0 via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:Solar_heater_dsc00632.jpg#/media/File:Solar_heater_dsc00632.jpg

Cooling renewable energy technologies are less available. For instance solar thermal cooling systems seem to exist mainly as large-scale technology; they tend to be complex to design and generally are quite costly. They are not considered in the STEPs project, which deals with the large-scale dissemination of medium scale collective or individual small-scale mature technologies.

Heat pumps imply dwellings of good quality with good insulation which is not a common occurrence in the case in poor communities.  Nevertheless ground-source heat pump could potentially be used at a larger scale (http://unu.edu/publications/articles/geothermal-energy-in-developing-countries-and-the-mdgs.html).


Energy-efficient insulation and passive housing have traditionally been the preserve of developed nations (for example, the developed German passive housing technology sector). However, the potential for efficient insulation and space temperature management with locally-sourced, low-cost renewable materials has been realised in a number of countries, particularly in Sub-Saharan Africa. This includes both traditional methods for adapting households in temperate developing countries, such as cladding and thatch roofing, as well as the more modern concept of passive housing, where thermal energy inputs (for example, from the sun) are used as part of the building’s thermal energy regime, enabling a reduction in the use of air conditioning methods.

Traditional housing for example in Lesotho is adapted to the variable temperatures of the mountain climate the country resides in, with rondavels (traditional huts) having conical thatched roofs and daubed exterior walls for insulation against the often cold climate, and warm air retention.


By K. Kendall (originally posted to Flickr as Rondavel, Gisela) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons

Business model examples and projects for efficient insulation in developing countries are few and far between. For instance, the iShack project in Enkanini, an informal settlement in Stellenbosch, South Africa in partnership with the University of Stellenbosch, is predominantly a fee-for-service solar home system project, where users pay a small monthly fee on top of a fixed installation cost for small (50-80W) solar home systems. However, the organisation is also expanding into sustainable insulation and other household services, particularly sustainable wastewater treatment and household-scale biogas installations for cooking.


Enkanini, Stellenbosch from the steps of the iShack hub. Image: Daniel Kerr

– Xavier Lemaire & Daniel Kerr – UCL

Second STEPs Network Meeting – KwaMbonambi, South Africa, 28-30 October 2014

The second STEPs network meeting was held in KwaMbonambi, South Africa from the 28th – 30th October 2014. The purpose of the meeting was to address the current status of the project and determine next steps, as well as take the opportunity to both meet local representatives from South African electricity and thermal off-grid concessionaires, and visit the operations of local concessionaires for fieldwork, which will be described in a later post on this blog.

The first day of the meeting saw a great deal of discussion among project partners as to the way forward for the STEPs project. Primary discussion focused around the construction of the STEPs model, focusing on five main aspects: institutional arrangements, business/enterprise models, financing, technology options, and policy/regulation. The project will look to test a number underlying assumptions for the sustainability of thermal energy service businesses, for example operating margins (in the 50-70% range), and the importance of using public sector clients as anchor consumers in a thermal energy business customer base.

Discussions were had on the most relevant technologies to target with STEPs. Key technologies are improved cookstoves, LPG for cooking/refrigeration, and household biogas installations, primarily for the successes seen in previous projects using these technologies. These include the Ghanaian experience in LPG stove dissemination via the government, and the vast scale of the Chinese domestic biomass gasifier program. However, challenges exist to the uptake of all these, including cultural contexts for cooking (meaning stove design needs to take social factors into account), as well as the difficulty in acquiring biomass feedstocks in some country contexts, for example Sub-Saharan/Southern Africa.

Discussion was also had about the most relevant financial and management models to target under the STEPs model, as well as which technologies these models applied best to. For example, outright/financed purchase models under a concession contract are most relevant for improved cookstoves, whereas fee-for-service and progressive purchase models are more relevant for LPG and biogas systems.


Binu Parthan presenting to the STEPs team – 2nd Steps meeting network – KwaMbonambi, South Africa – 28th – 30th October 2014.

The second day saw representatives from local utility concessions in KwaZulu-Natal attend the STEPs meeting. The concessions represented were KES, with their CEO Vicky Basson attending, active in the Durban and central KwaZulu-Natal region, and Nuon-RAPS (NuRa), with MD Sifiso Dlamini, active in Northern KwaZulu-Natal up to the Mozambican border. The KES utility was founded in 1997, and currently services over 28,000 customers with solar home systems on a fee-for-service basis in and around the Durban area. Tariffs are set at 96ZAR/month for a solar home system, with six lights (2 outdoor, 4 indoor), and a 9V and 12V DC connection point. The company has provided LPG services, both in LPG bottles and integrated stove systems (notably the Shesha stoves from Totalgaz). Their concession is granted via a bidding process by the KZN state government and local municipalities on a yearly basis.

Questions were answered by the concessionaires that added context to the construction and future work of STEPs. These included revisions of assumptions for sustainable operating margins, insight into the regulatory framework in South Africa for LPG financing, and particularly the barriers to the use of mobile money in South Africa, due to transaction regulations in the financial sector and a lack of culture for mobile payments. Subsidy positioning from the government was also identified as a key barrier in South Africa to thermal energy use, with subsidies moving between thermal energy sources frequently.

Both concession representatives stated a desire to expand their thermal energy services business, and stated the criticality of tailored solutions to national and local contexts for technologies, an aspect of the thermal energy market that is core to the development of the STEPs model.


Discussion between the STEPs team and Vicky Basson (KES, far left) and Sifiso Dlamini (NuRa), middle – 2nd Steps meeting network – KwaMbonambi, South Africa – 28th – 30th October 2014.

A number of conclusions were drawn from the meeting. Given the ongoing political difficulties in Lesotho, a reorientation of project objectives was proposed to take into account the changing landscape in which the project operates. Current goals are to construct the STEPs model as a resource across all sectors, being relevant to governments and policy-makers, as well as the private sector and SMEs/entrepreneurs wishing to enter the thermal energy services market.

– Daniel Kerr, UCL Energy Institute