Cost and reliability of solar pumps in Mali?
HI All
Are solar pumps generally regarded as good or not, eg in terms of value for money, being prone to failure etc?
What sort of price might you expect to pay for a solar water pump and borehole (to a depth of around 100m) in rural Mali?
If you were to add on two water storage tanks also, is £40k a very expensive amount in total?
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3 Answers
This answer comes from my new colleague Mary Allen - Practical Action West Africa office.
Are solar pumps generally regarded as good or not, eg in terms of value for money, being prone to failure etc.?
You don’t say what the water is for. We have assumed it’s for general household/domestic use as you are pumping from 100m
Yes – solar pumping a commonly selected option if the size of the community and/or value of activity can meet the repair and maintenance charges including pump, solar panel and other part replacements in line with manufacturer’s recommended lifetimes if these are less than 20 years (for water supply the community is not expected to fund replacement of the borehole design life 20+ years). Govt. policy in Mali is to install pumped piped water supplies (generally solar) for villages 2000 inhabitants or more. For villages below 1500 in habitants you need to look carefully at lifetime costs, work out how much people need to be paying per bucket and check they agree to this. Don’t budget for them to purchase more than 5 litres of clean drinking water per person per day (even though the norm is 20l).
If you are pumping from 100m an electric submersible pump may be your only option so your choice will be between solar or a diesel generator. Hand pumping from this depth would be very difficult. In Senegal if the discharge from the water table is high enough, they install the borehole and pump in a central location and pipe water to 6 or more small villages at a time. This takes more sophisticated organisation but gets over the costs issue to some extent
In terms of breakdowns – the panels are generally reliable if purchased from a reputable dealer and installed by qualified staff. The main risk is theft. The pump and electrical components will need regular maintenance and repair/replacement. You should check that parts and qualified maintenance staff are available in the area. There is an organisation (STEFI I think it is called) which takes on the supervision of this in some areas for a % of the water fees collected
Please note that in Mali all installation of water supplies for domestic use, should go be done via the elected local government structure (rural commune) who according to law are the owners (“Maitre d’Ouvrage” )
What sort of price might you expect to pay for a solar water pump and borehole (to a depth of around 100m) in rural Mali?
If you were to add on two water storage tanks also, is £40k a very expensive amount in total?
I have never seen a solar pump without a storage tank – usually elevated (water tower) so that gravity does the rest. The prices I have below all include water storage tanks
The actual cost will vary considerably depending on the location of the village, the type of rock/subsoil you are drilling through and depth to water table, the diameter ...
Deciding whether a particular technology like a solar pump is suitable in a particular context can be determined with the Technology Applicability Framework (TAF) developed by the WASHTech Project.
The TAF was used to assess solar pumps in two districts in Uganda. WASHTech published technology recommendations for solar pumps in the 2 districts as well as separate case study assessments for the 2 districts: Kanungu and Ajumani.
An assessment for the introduction of solar pumps in Ghana will be published shortly on https://washtechnologies.net/
Solar pumps are an excellent solution for off-grid pumping. As always, you need good quality kit (Grundfos are very tough but we've also used Mono with good results), a proper design - matching head and flow to pump and PV array sizing - and an installation crew who know what they are doing. Once in, they run for years with no need of fuel and minimal maintentance. In general, they should last much longer than an engine based system because there is less to go wrong and far less need for operational input. Unless someone nicks the solar panels, which can be a significant risk if the pump is remote and locals don't have a strong sense of ownership of the system. A combination of local involvement / 'buy-in' and security measures - fixings and fencing should minimise the risk.
£40k could be a reasonable cost for the whole job, but it depends a lot on the head and flow required - do they want 500 litres/day or 50,000 ? I have no idea about drilling costs in Mali, and these again will be dependent on the borehole size and the geology, which in turn dictate the type of drilling rig and lining, and the time required.
You need at least to specify total static head, pipeline distance and daily water requirement to get a reasonable estimate of the system cost (excluding the borehole).
Best regards,
Duncan
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Depending on the total assessment, I believed £40k is too expenses. We can do better than that.