Solar energy for farms and agriculture

In an urban home the question is how much you save. On a farm it is often whether there is power at all. The grid may not reach, may arrive with frequent outages, or may arrive with a service connection whose extension cost exceeds that of the solar system itself.

That changes the decision frame. When the alternative is a diesel pump, the analysis is not about a return against the electricity tariff but about replacing fuel, transporting that fuel to the property, maintaining the engine and the hours of work spent looking after it.

And when the alternative is having no power, the comparison is against the loss: milk that is not chilled, irrigation that does not happen at the right point in the cycle, or a poultry house with no ventilation.

Pumping water with solar energy removes the fuel cost of diesel pumps and reduces maintenance. It is especially useful for irrigation, livestock watering and rural community water systems.

It also has a fortunate overlap: water demand is highest precisely when there is most sun and most evapotranspiration. The system produces when it is needed, which greatly reduces the need for electrical storage.

The system is sized according to the required flow, the total pumping head — which includes the height difference and friction losses in the pipe, not just the depth — and the peak sun hours available. A frequent mistake is to size only by the depth of the well and ignore the horizontal run to the delivery point.

There are DC solar pumps that connect directly to the array, with no inverter or batteries, using a controller that starts them when there is enough radiation. They are the simplest and most robust configuration when the use allows pumping during the day only.

In pumping there is a decision that often goes unnoticed and that saves a lot of money: storing water rather than storing electricity.

An elevated tank with capacity for two or three days of consumption performs the same function as a battery bank — having the resource available when the system is not producing — but with no service life limited by cycles, no degradation, no electronics and comparatively trivial maintenance.

Whenever the use allows it, the rule of thumb is clear: pumping during the day into a tank and distributing by gravity is cheaper and longer-lasting than pumping at night from batteries. Electrical storage is reserved for what that solution cannot cover.

Milk chilling, product preservation and cold rooms are loads that cannot tolerate interruption and that also have demanding start-up peaks.

Here storage is usually necessary, because refrigeration has to be sustained outside daylight hours. And there is an important technical nuance: what decides whether the system can start a compressor is not the energy available in kWh but the instantaneous power in kW. A bank with plenty of autonomy may still fail to start the equipment if its power output is insufficient.

So it is worth sizing against the equipment's real start-up peak, and considering whether a soft starter reduces that demand. It is one of the most common causes of rural systems that disappoint despite being correctly sized on energy.

Unlike the urban setting, on many farms the grid is intermittent or non-existent. There, hybrid systems with batteries provide real autonomy for critical processes such as refrigeration or milking.

Storage is sized for the priority loads, not necessarily for the whole farm. The exercise is to list what has to keep running and for how long, add up the power ratings to know what can be switched on at once, and add up the energy to know how long it lasts.

In areas genuinely without a grid, the system is off-grid and the battery bank stops being backup and becomes the only night-time source: cycling is daily and deep, and that clearly favours lithium over lead-acid despite its higher up-front price.

Sustained rural heat and poorly ventilated enclosures shorten the life of any chemistry, so where the bank is located — in the shade, ventilated, never under uninsulated sheeting — has a real effect on how many years it lasts.

The agricultural environment is harder on equipment than it looks, and that has to show up in the specification.

Dust from soil work and from unpaved roads settles on the glass and, with no rain to wash it off, reduces output persistently: cleaning frequency in the countryside is higher than in the city. In installations near poultry houses or stables, the presence of ammonia calls for modules tested for that environment. And near the coast, salinity adds to it.

There is also an access factor: on a farm, the nearest technician may be hours away. That makes the robustness of the equipment and the simplicity of the design worth more than a few tenths of efficiency, and turns remote monitoring — where there is coverage — from a convenience into a necessary tool.

A rural particularity: the distance between where the panels are best placed and where the consumption is tends to be far greater than on an urban roof.

That distance has electrical consequences. Conductors have to be sized so voltage drop does not eat into the output, and it is sometimes cheaper to carry alternating current at a higher voltage than direct current along the whole run. It is a design decision with a direct impact on cabling cost, which in these projects stops being a minor line item.

And where there is frequent atmospheric electrical activity — common in many rural areas — surge protection and a properly resolved earthing system stop being optional.

The agricultural sector has credit lines aimed at productive investment that can be applied to energy projects. It is worth checking which ones are in force at the time of investing, because terms and quotas change.

If the project is structured as productive investment and the investor files income tax, the benefits of Laws 1715 of 2014 and 2099 of 2021 also apply, with the corresponding certification from UPME.

A well-planned solar system also provides stability against fuel price volatility, which on a remote property includes the cost of transporting the fuel there.