Solar Power for Farms in Ghana

The diesel pump that eats the profit

Ask a vegetable grower near Kasoa what the pump costs, and the answer comes in fuel drums rather than in cedis. A small petrol or diesel pump runs for hours in the dry season, hauling water from a well or a borehole to a tomato plot, and every tank of fuel has to be bought, carried and poured. When the fuel price moves, the margin on the crop moves with it. When the pump breaks, the crop waits.

Solar can take much of that load off a farm, but only for the jobs that match the sun. A panel makes power in daylight. It does not make power at night, and it does not make a lot of power on a dusty or cloudy day. The farms that do well with solar choose the loads carefully, size the system to them and store water or energy where the timing does not match.

This guide is about the whole farm. Poultry houses have their own solar questions, and our guides on solar for a poultry farm and generator, solar or inverter for a poultry farm go into the layer and broiler details. Here we look at pumps, fences, drying, cold storage and milling, and at what each one asks of the sun.

Where solar earns its place on a mixed farm

Solar does not pay back equally well on every job. The best candidates are the loads that run in daylight, that are steady and that you now buy with fuel or with someone else's electricity. The table below ranks the common farm uses by how well they usually suit solar, with notes on what each one needs.

Start with the first row. Pumping is usually the largest daily saving for crop farms, and it is the job that the sun does best. The other uses can follow once the pump is paying its way.

Pumping from a borehole: a worked example

The power a pump needs to lift water depends on how much water you move and how high you lift it. In metric terms, the hydraulic power in watts is roughly the flow in cubic metres per second, times the lift in metres, times 9,810. The pump itself is not perfect, so the electrical power you need is larger than the hydraulic figure.

Take a simple case. Your pump moves 3 cubic metres of water an hour, which is 0.00083 cubic metres a second. The total lift from the water level in the borehole to the tank is 25 metres. The hydraulic power is about 0.00083 times 25 times 9,810, which comes to roughly 200 watts. Assume the pump and its controller together run at about 45 per cent overall. The electrical power drawn is then roughly 450 watts.

Run the pump for five hours a day and it uses about 2.3 kilowatt-hours of electricity. A panel array in Ghana is usually planned on about 4.5 to 5 peak sun hours a day as a starting figure, lower in the rainy months. Allow about 25 per cent for losses in wiring, dust and heat. The array needed is then roughly 2.3 divided by (5 times 0.75), which is about 0.6 kilowatt-peak. Choose a little more, around 0.8 kilowatt-peak, so that the system still pumps on a dusty day and as the panels age.

Treat these numbers as a method, not a quote. Your pump maker publishes a performance curve for each model, and your installer should work from that curve, from the real lift in your borehole and from the water level you measure in the dry season, not the wet one.

Store the water, not the electricity

For irrigation and livestock water, a tank is almost always a cheaper battery than a bank of lead-acid cells. Pump in the sun, fill a tank, and let gravity deliver the water at dusk. That way the system needs no battery at all, and the water is there when the crop or the animals need it.

The tank has to be big enough for the day's water. In the example above the pump moves 15 cubic metres in five hours, which needs a tank or a set of tanks that holds at least that much. If the tank cannot hold a full day's water, either the pump has to run in the hours when the crop uses the water, or the irrigation has to match the pumping window. A common mistake is to size the pump for the bore and forget the tank, so the water runs over the top in the early afternoon and the plants get nothing at the hottest time.

Use a float switch or a level sensor so the pump stops when the tank is full. Our guide to boreholes and irrigation explains how to find the yield that the pump must match. Dry running will burn out a submersible pump, and a repair in the middle of the dry season is expensive in time as well as money. Ask the installer to show you how the controller stops the pump in both cases, and test it before you leave the site.

Fencing and security with a small solar system

An electric fence is one of the cheapest ways to keep animals out of a crop and to stop goats from wandering into the vegetable plot. A solar energiser runs off a small panel and a battery, and it needs very little power. Its output is rated in joules and its fence length in kilometres. Match both to the fence you are building, and buy the energiser from a dealer who can show you the rating in writing.

The fence has to be earthed properly to work. Most failures are not in the energiser at all. They come from a poor earth rod, weeds touching the wire or a gate that breaks the circuit. Walk the fence after the first rain and after any grass cutting, and check the voltage at the far end with a tester.

Security lights run well on solar, provided they are mounted where the panel sees the sun and the lights are switched off during the day. A motion sensor saves battery. Keep the light away from the poultry houses if you do not want the birds woken by a light on a timer, and check that the battery is sized for the number of hours you need.

Solar drying for grain, cassava and chilli

Drying is where solar can protect a harvest rather than merely cut a bill. Maize, groundnuts and cassava chips that are dried thoroughly keep longer and carry less risk of mould. Mould, and the aflatoxin it can bring, is the reason buyers reject damp grain. A simple solar dryer uses a black-painted collector to warm the air and a fan or a chimney to move it through a bed of produce.

The design matters more than the panel. A dryer with poor air flow cooks the produce on the outside and leaves the middle wet, which is the worst result. The fan should move air through the bed rather than over the top of it, and the produce should be spread thinly enough that the air can reach every piece. Test a sample by weighing it before and after drying, and check the moisture with a meter if your cooperative or buyer uses one.

Keep the drying area clean. Dust, animal droppings and dirty trays can spoil a clean crop faster than damp ever could. Our aflatoxin guide explains why contamination matters for animals fed on grain, and the same care applies to the grain you sell.

Cold storage on a small farm: what it really takes

A cold room for tomatoes, leafy vegetables or fish is one of the most attractive ideas in solar, and one of the easiest to size wrongly. The compressor runs for many hours a day, sometimes around the clock, and its draw is the largest steady load on most small farms. A battery big enough to carry it through the night can cost more than the panels, and it will need replacing before the panels do.

The honest question is whether the cold store earns more than it costs. Work out how many kilogrammes of produce it saves from spoiling, what that produce would have fetched on a normal day and how many days a year you would use it. Then compare that gain with the battery replacement and the maintenance on the compressor. A small cold store that keeps a crop for two extra days may be worth it in a market town and not worth it on a remote farm with no buyer.

Ask the installer for the daily energy use of the cold room at its rated power and its duty cycle, which is the share of time the compressor is actually running. Ask for the battery's expected life in years, not only its warranty period. Check the figures with a second opinion if the installer cannot show the working.

Milling, grinding and the big motors

A grinding mill for maize, cassava or feed is a different load from a pump. It draws a large surge when it starts, and it runs for an hour or two at a time, so the inverter and battery must be able to deliver that surge without tripping. Many small mills are rated on a motor size that looks modest but starts with several times the running current.

Check the starting current in the motor's specification, not only the running power. Tell the installer how many hours the mill runs in a day, and whether you grind in one session or several. A farm that grinds once a week for a few hours may be better served by a generator for the mill and solar for the pump, rather than a battery sized for the mill's start-up surge.

Keep in mind that a large mill is usually the job that makes diesel and petrol back-up sensible. A hybrid system, with solar for the daytime loads and a generator for the mill, is often the cheapest way to avoid buying a larger battery than the rest of the farm needs.

Reading the sun against the crop calendar

The sun is strongest in the months when the crop needs the most water, which is a convenient match for a solar pump. In the dry season the days are long and clear, the pump runs at full output and the irrigation demand is high. In the rainy season the panels make less power on cloudy days, but the crop needs less pumped water because the rain is doing the work.

The harmattan changes the picture for a few weeks. Dust settles on panels, and the air is dry enough that a crop on a light sandy soil needs more water than usual. Clean the panels more often in that window, and plan the pump hours around the drier days rather than the cloudy ones. A simple dust-cleaning routine, with a soft brush and clean water, keeps output steady without damaging the glass.

Keep a log of the pump hours, the tank level and the cleaning dates. A year of records shows you whether the system is over-sized, under-sized or just right, and it gives your installer something concrete to work from when you ask for a change.

Buying from a licensed installer

Anyone carrying on commercial renewable energy work in Ghana needs a licence from the Energy Commission. The licensing rules sit under the Renewable Energy Act, 2011 (Act 832), and the Commission's notice covers solar installers along with importers, distributors and retailers. Operating without a licence is an offence, so ask the installer for the licence number and check it with the Commission before you sign.

A licensed installer should give you a written design, showing the panel count and rating, the battery size, the inverter or controller, the cable runs and the expected output in your location. Ask for the design in writing and check that the numbers match what you asked for. A quote that names only a price and a kilowatt figure is not a design.

Ask about the warranty on each part, and who you call when the panels fail or the controller stops. A warranty from an importer who has since left the country is not a warranty. Check whether the installer has a service office within reach of your farm, because a pump that is down for three weeks in the dry season costs more than the part.

The Energy Commission has also published a net metering code for grid-connected systems. If your farm is on the national grid and you plan a grid-tied system, ask about the code's current terms, because the rules for selling power back to the grid are different from the rules for a system that runs only on your own farm.

Where the poultry side fits

Halaal Farms is a day-old chicks hatchery, so our solar questions are mostly about the hatchery rather than the crop. The lesson we would pass to any farmer is that a poultry house and a pump have different needs. Lights, fans and a water pump in a house are steady loads that run for many hours, and a brooder that needs heat through the night is the hardest job for solar on its own. Our guide to brooding without electricity covers that part of the problem honestly.

If your farm keeps poultry alongside crops, the same panel can serve both. A daytime pump for the vegetables and the drinking water tank for the birds, with a small battery for the house lights, is a sensible split. The house itself still needs the right backup for a power cut at night. Our solar guide for a poultry farm works through the house loads in detail.

When you are ready to stock the house, our day-old chicks range is the place to start, and the prices page lists the current starting prices. For longer arrangements with farmers who are building mixed systems, see how we work with farmers.

A checklist before you buy

Take this list to every installer you consider. A good installer will answer each line without fuss, and a poor one will change the subject.

• The installer holds a current licence from the Energy Commission, and you have the licence number in writing.
• The loads are written down: pump, fence, drying, cold store, lights, mill, with the hours each runs per day.
• The borehole or well has been measured for the dry-season water level and the total lift.
• The pump curve, controller model and float switch are named in the design.
• The tank holds at least one full day's water, or the irrigation matches the pumping window.
• The battery size, expected life and replacement cost are shown, if a battery is part of the design.
• Each part has a written warranty, and the installer has a service contact within reach of the farm.
• A cleaning routine and a monthly log of pump hours and tank levels are agreed before the system goes in.

If the installer cannot tick a line, ask them to show the working before you pay a deposit.

Questions farmers ask