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

References

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

Solar Cooking and Energy Service Companies: An Unexplored Market Opportunity?

Solar cooking, as a technology and group of products, has existed for many decades, with examples being used in the 1970s. The technology in its simplest form has remained relatively unchanged since then, with the basic premise being either a flat or parabolic reflecting surface, placed in the sun, reflecting sunlight onto a cooking chamber. This can be either below the flat-plate reflector, or at the focal point of the parabolic collector. These types of devices are easy to manufacture and can be extremely cost-effective, with little more than a reflecting surface (for example, foil-backed card) and a cooking vessel needed for a minimum setup. These features give this technology particular applicability for targeting bottom-of-pyramid consumers with sustainability interventions: typical prices for simple designs (such as the flat-plate reflector shown below) range from US$3-5.

Solar box cooker made from carboard boxes and aluminium foil. Image: https://nakazora.files.wordpress.com/2011/06/solar-cooker1.jpg

Parabolic solar cooker in use at an informal settlement in Barcelona. Image: Brinerustle / Wikimedia Commons / CC BY-SA 3.0

 

A number of companies currently distribute simple kits for creating solar cookers from scratch, usually in the form of a reflective card template for the reflecting surface. However, these pre-packed kits are often more expensive than locally-sourcing materials for manufacture, ranging up to US$30-40, without offering meaningful benefits to the consumer aside from convenience. There are also a number of companies in developing countries that distribute full solar cookers to consumers using a direct-purchase business model, such as SunFire in South Africa and L’Obel Solar Power in India. Prices for these designs, commonly higher-quality parabolic mirror cookers, range up to US$200.

As such, it appears there is an opportunity for low-cost solar cooking business to develop markets for cheap, reliable solar cookers for bottom-of-pyramid consumers. In addition, through using alternative payment models for business, higher-cost designs can become more accessible to a greater number of consumers. Offering micro-credit products for deferred purchasing of solar cookers, or engaging with consumers on a fee-for-service basis with consumers paying a monthly fee for their product, would allow mid-range technologies to become accessible to consumers with lower incomes.

Other opportunities exist in the solar cooking market space for complimentary technologies, in particular heat-retention bags such as the Wonderbag from South Africa. This is designed to fit around the cooking vessel to retain heat and slow-cook the contents, after it has already been heated, reducing the overall energy requirement for cooking. Whilst this technology is perhaps most applicable to wood or charcoal-fired stoves, it can also help improve convenience when using solar cooking products. For example, rather than leaving a cooking vessel in the solar cooker for up to six hours, it can be left there for 1.5-2 hours, then transferred to the Wonderbag for further cooking.

For more information on the Wonderbag and use-case studies, please refer to https://samsetproject.wordpress.com/2017/04/10/energy-poverty-in-peri-urban-communities-in-polokwane-south-africa-part-1-identifying-the-issues/

— Daniel Kerr, UCL Energy Institute

References

Teach A Man To Fish (2009) Solar Cooker Business Guide. Available at: http://www.teachamantofish.org.uk/resources/incomegeneration/Solar-Cooker-Business-Guide.pdf

Gautam (2011) Microfinance Intervention for Financing Solar Cooking Technologies – Financing With Savings. Available at: http://www.microfinancegateway.org/sites/default/files/mfg-en-paper-microfinance-intervention-for-financing-solar-cooking-technologies-financing-with-savings-mar-2011.pdf

Solar Cookers International: CooKit. https://shop.solarcookers.org/?pn=CooKit&cn=Solar+Cookers&p=621&c=27

L’Obel Solar Power Systems: Solar Thermal Products: http://www.lobelpower.com/solar_thermal_product.htm

SunFire Solutions: http://www.sunfire.co.za/wp/

Wonderbag World: http://www.wonderbagworld.com/