Post-harvest food loss compromises food security, farmers’ livelihoods and the environment. Cold storage can significantly reduce post-harvest losses, enabling farmers to keep produce for longer, aggregate together, and improve profits by accessing higher-value markets. However, cold storage facilities are inaccessible to most rural, off-grid farming communities in Uganda.
Our innovative solution
SVRG have partnered with EcoLife Foods, an NGO based near Kampala to develop a solar-powered, low-cost, sustainably built and locally sourced cold store as a part of the Efficiency for Access Research and Development Fund
SVRG and EcoLife Foods developed this idea further with Kiima Foods, a community NGO based in Kasese, Western Uganda. Within our IMGAL project, the cold store is an integral part of the Farmers Enterprise Centres (FECs), which have been designed to meet the needs of local farmers.
Find out more about our innovative project design…
Using solar energy and energy storage by batteries means our cold stores can be built where needed most- in rural communities with agriculture-based livelihoods. Once a cold store has cooled, the excess solar power can be used to power a range of energy-productive enterprises for the community around the cold store.
Interlocking Stabilised Soil Bricks (ISSBs)
ISSBs are an innovative construction method which use much less cement than traditional clay-fired bricks in both the making and laying process of them.
Soil and approximately 5% cement is mixed together and pressed together using a brick press. A key benefit of using ISSBs is that they can be locally made, and people from the communities are trained in making these blocks, a skill which can be utilised after construction of the cold store.
Less cement = less embedded carbon in the construction process and less environmental impact!
In our project in Mbata, 24 youths were trained to make ISSBs, and they are now sharing their knowledge with youths at a second site in Mukorokumi.
Optimised thermal insulation
Cavity wall construction
Using two layers of ISSB bricks in a cavity wall configuration means insulation can be used between them. ISSBs are excellent insulators in their own right, hence using a double layer ensures that the cold store stay cool. Rice husks are placed in the cavity between the two ISSB walls in sacks.
Locally sourced insulation from waste material
Rice husks are a waste materials which are low cost, readily available, have high thermal performance and a better resistance against weevils and mould. They also performed comparatively far better thermally in comparison to other waste materials which we tested.
We take great care to arrange the insulation carefully, to ensure there is a continuous layer all around the cold store and the ceiling, to avoid a thermal bridge where heat transfer could occur.
Careful temperature control
By putting up simple partitions, the temperature throughout the cold store can be staggered. Partitions work by breaking up the airflow, meaning we are able to lower the temperature down to 5 degrees at one end and 12 degrees at the other.
Water as thermal mass
Whilst the ISSBs and rice husks provide a great thermal barrier, we also have another low-cost way of enhancing insulation. Filling jerry cans with water (+ a little bleach), and placing them around the edge of the cold store increases the thermal mass of the space.
The thermal massiveness is a measure of an internal space to change temperature. Since water has high thermal mass, it takes over four times more heat energy to raise water by 1 degree than concrete or bricks. These jerry cans act as an extra cold ‘weight’, through delaying temperature change, for example when warm produce is brought into the cold store to cool down.
Temperature and humidity sensors give us real-time data so we can see the temperature, relative humidity, dew point and vapour pressure deficit of each partition of the cold store to see how our produce is doing.
Weather stations on the outside help us understand how the solar panels are performing relative to the external conditions. For example, if there’s a lot of sun, we expect a lot of power and if not, we would take the necessary action e.g. cleaning them.