Sourcing material in Uganda for solar heaters, biomass generator and
other smaller projects.
I am responding to your question because solar water heating is an area of fascination for me - not from a position of expertise but my answer may help to focus your search.
I think this is the location you are talking about - an initial search proved wrong so this link may help others. https://maps.google.com/maps/ms?ie=UTF8&oe=UTF8&msa=0&msid=211146633784452719252.0004b93fc21c89d0e17af
Kumi Hospital appears to have had a lot of work done on it in recent years, apparently having been an IDP camp in the 90's. If so then on the basis that others have been doing a lot of rehab and extension work in recent years then getting materials to site will not be an issue. To raise your confidence about this you could find out some more information on the rehab and extension work to find out who the contractors were and ask them.
You have mentioned three projects: raising a water pump, a biomass generator and solar water heating and want responses to the last one. Quickly addressing the first two: I am confident that you can get some advice on this forum about raising the water pump. A biomass generator via gasification would be interesting or is this a bio-gas plant? I found this on REEP's site: https://www.reeep.org/projects/setting-innovative-jute-processing-using-biomass-based-electricity-india
Turning to the solar water heater: I had a quick scoot around and found this https://www.reeep.org/projects/promotion-solar-water-heating-uganda who should have papers available on their findings. Paging through the solar project investigations performed by REEP it appears that South Africa is ahead of the game. In your shoes I'd be looking to import a panel and header tank system purpose made rather than make it myself. Alternatively REUK has some information on this and there is a bunch of information and idea links here: https://www.builditsolar.com/Projects/WaterHeating/water_heating.htm
You may find a few workshops already making solar water heating panels in Uganda - there was one setup in Kigali Rwanda around 2007 but I think they were importing panels from Israel. The university in central Kigali (KIST) was into solar water heating and may be able to help as well.
One thing to be careful of in heating water is any risk of legionella. The prime method of control here in the UK that I am aware of is to ensure that the water from cold outlets is <20C and from the hot outlets is >50C (and am happy to be shot down about this rule of thumb). Certainly you should be careful to avoid vented tanks full of hot water - far better to keep the system pressurised and unvented but then you are into pressure vessel regulations / maintenance of pressure relief valves and corrosion concerns.
I found a couple of contacts here: https://energy.sourceguides.com/businesses/byP/solar/solar-water-heating/byGeo/byC/Uganda/Uganda.shtml
eg: Sunrays solar Energy
Business type: retail sales, importer Product types ... (more)
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