by Conrad Roedern
The lament “Solar is too expensive” does not hold water any more. Solar power has become much more competitive within the last years. Let me start with photovoltaic solar water pumping, often abbreviated as PVP: While some years ago only boreholes with a shallow water table (typically less than 70m) and low daily yield (typically 10 cubic meters or less @ 70m head) had been economically feasible Solar pumping can now fulfil all requirements in terms of volume and lifting head. This stems from the fact that today solar electricity can be produced much cheaper on site than delivered by a Diesel generator or even sourced from Namibian electricity grid. Highly efficient submersible pumps are available which can be run directly from the panels or – in case of emergencies – from a small AC generator. But it can also make sense to convert traditional shaft-driven MONO pumps to run directly from solar power (with no batteries involved) while keeping the typical LISTER engine just as a backup. Swopping is easy: One just changes V-belts back to the LISTER.
But why only looking to water pumping? Running a farmstead on solar power now makes perfectly sense when it comes to sites which are already grid-connected but definitely for those which operate “off-grid”. For the case of “on-grid-farms” the solution is a so-called PV feed in system which is available for both single-phase and 3-phase clients. Electricity consumers become “prosumers”. During sunshine hours the system feeds directly all appliances of the client while excess power goes back into the electricity grid; the grid acts similar to a battery which “buffers” differences in supply and demand. The excess will be compensated under “net-metering” (from July 2016) legislation as a non-cash credit to be used again during night time or when the solar power is not sufficient. Off-grid systems have benefitted from the strong fall in panel price (down to 30% of what it was four years ago) as well. Farms and lodges typically run on a hybrid system where hybrid means running from two energy sources: e. g. Solar and Diesel. Since Solar can produce cheaply the fraction still to be produced by Diesel will typically go down to below 10%. Night-time power comes from a professional deep-cycle battery set which easily lasts for 10 to 15 years. Maintenance-free Lithium-Ion batteries are on the doorstep and will become cost competitive soon.
What else helps the “Solar Revolution” to become reality? Ultra efficient appliances have become available, especially when it comes to lighting and refrigeration. Even modern energy saving bulbs – “CFLs”, saving up to 80% if compared with incandescent bulbs and having been accused for their, in comparison with traditional fluorescent lights, minute mercury content – finding now strong competition in LED-lighting. LED-lights last about 5 times longer than good CFLs (some 50000 hours) and pose even less threat of environmental contamination. But watch out: since LED technology is still expensive and coming in all sorts of qualities you should lay emphasize especially on long service life, good light colour and low power consumption. Today’s high quality fridges, freezers and cool rooms consume less than half of the energy of their low-cost conventional predecessors. Look for fridges, freezers and combinations which carry efficiency labels like “A+” or even “A+++”. Made in Namibia: Energy-saving cool rooms with soft-start and extra strong thermal insulation can be sourced locally. Their reduced power and energy requirements allow them to run even on medium sized solar systems.
Small is beautiful: new technology also found its way to solar home systems (SHS). So-called pico-SHS satisfy the basic demand for lighting, cell-phone charging and playing a radio. They normally come as DIY-kits. But please watch out: only quality systems are using long-lasting LED hanging lights with switches, a lithium-ion battery (no lead or cadmium anymore!) and a powerful cell-phone charger which is able to even fully charge a smart phone. Accessories and repairs should be available locally.
Going Solar means savings from day one! Clean Solar power – cheaper than grid power – can be seen as the great game changer towards Harambee prosperity for all Namibians!