Following our previous post on heating, this last post will investigate other energy service needs linked notably to farming activities.
Refrigeration in developing countries in remote areas is rarely found except for specific needs like to keep vaccines for health centres. A number of possibilities exist to provide refrigeration with LPG, with passive solar, and again using ground-source heat pumps, but it seems solar PV is the most economical one. Various attempts have been made at renewable refrigeration over the past 30 years, predominantly focusing on solar collector designs, although photovoltaic vapour compression systems are the most commonly found for vaccine refrigeration. The high cost of these systems can often be justified by the importance of the application.
Larger refrigeration systems based on solar collection/kerosene/LPG power using different absorption refrigeration cycles (for example the Platen-Munters ammonia-water-hydrogen continuous diffusion absorption cycle) have been tested for ice-making in developing countries, but the lack of constant heat sources in renewably-powered systems has made reliability and efficiency a concern. Alternatives do exist to LPG-powered refrigeration in the form of solar refrigeration however, and with the current global lowering of photovoltaic and other solar components, the technology is becoming more cost-effective and viable to small entrepreneurs.
Platen-Munters absorption refrigeration system and cycle. Image – centrogalileo.it
Drying is to be found in agriculture, but not at a small scale for individual households. Tray design solar dryers can be useful for small agricultural businesses to increase productivity, and are often easy to construct from locally-sourced materials. Updraft-style solar dryers are more complex from a design perspective, requiring specific attention to be paid to air flows and moisture extraction from the heating areas.
Solar drying for chilli pepper crop in Peru, with locally-produced equipment. Image: Carlos Bertello, GIZ EnDev Peru.
Other Agricultural Uses
Milk pasteurisation is a critical issue for dairy farmers in the developing world. It has been estimated that over 50% of an average rural dairy farmer’s milk crop in Kenya will spoil before it has been sold, which has a severely detrimental effect on their livelihood and income generation. Modern pasteurisation equipment using steam boilers and batch-type pasteurisers can significantly increase output and income from a rural dairy farm in the developing world.
These steam boilers can be renewably powered, for example through biomass from animal/crop waste. Low-temperature (70-80°C) water can be substituted for steam in the pasteurisation process with only slight plant modifications, and this allows the potential for greater renewable energy use in the process, for example through flat-plate solar collector water heating, or cogeneration/recuperation from electricity generation or refrigeration equipment condensers. Whilst renewable pasteurisation technology has not been a focus of many organisations, the FAO have produced a report on the potential uses and processes for the technology, which is available here (http://www.fao.org/docrep/004/t0515e/T0515E03.htm).
Potential for novel pasteurisation technologies in the developing world, to be powered by renewable electricity from solar or biomass digesters. Image: Openideo, Sarah Rizk, Stanford University.
In conclusion of this series of three posts, there exists vast potential over the wide range of available thermal energy services for the residential, industry and commercial sectors, notably in the Global South in general, and Sub-Saharan Africa specifically. The STEPs project will specifically be working most on the services that appear most viable in the Sub-Saharan African context: cooking/heating services for household needs, and low-temperature hot water production for households. The need for sustainable cooking and household thermal energy is a pressing one, and the STEPs project, through investigating a technology-neutral approach to thermal energy services and business, hopes to address this need.
– Xavier Lemaire & Daniel Kerr – UCL