Solar for Farms, Water Pumps and Remote Sites

Most solar articles assume a house with a grid connection and a bill to shrink. Plenty of the work we do isn't that. It's a pump on a field, a hut with no line running to it, a site where the utility quoted a number to extend the line that made solar look cheap by comparison.

The engineering is different, and so is the way you should think about the money.

The economics flip

On a house, solar competes with an electricity tariff. On a remote site it competes with the cost of getting power there in the first place: poles and line extension, or a generator plus fuel forever, or simply doing without.

Once you frame it that way, payback stops being the right question. When the alternative is a quotation for line extension that runs into hundreds of thousands, or hauling diesel up a track every week, the comparison isn't close.

Water pumping: the happy case

Solar pumping is one of the neatest fits in the whole field, for a reason that isn't obvious until someone says it.

You store water, not electricity. Pump into a tank when the sun's up, draw from the tank whenever you like. The tank is the battery, and it's enormously cheaper than a battery, doesn't degrade in five years, and needs no management system.

So a well-designed solar pump often has no battery at all. Panels, a pump controller, and a tank sized for a couple of days of demand so a run of grey weather doesn't leave you dry.

What the design hinges on

• Total head, the vertical lift from water level to outlet, plus friction in the pipe. This drives the power requirement more than volume does.
• Daily volume you actually need, in cubic metres, for irrigation or livestock or household use.
• Tank capacity, ideally two days or more of buffer.
• Surge at startup. Motors pull hard for a moment when they start, and the controller has to cope. Undersize this and the pump simply won't start on a cloudy morning, which is exactly when you'll notice.

Off-grid for buildings

A farmhouse, bunkhouse or processing shed is a harder problem, because here you really do need to store electricity. The design has to survive several consecutive overcast days, so it gets built around the worst week of the year rather than the average one.

Which means being ruthless about the load list. Every appliance is a line item:

• Lighting and phone charging: trivial, always included
• Refrigeration: significant, usually essential, and it runs all night
• Pumps: big surge, best run in daylight if they can be
• Welding, milling, workshop tools: intermittent but heavy, size the inverter for them
• Electric heating of anything: almost always the wrong answer off-grid

Cutting the load is nearly always cheaper than generating more. An efficient DC fridge instead of an old chest freezer can save more money in battery than it costs to buy.

Where a generator still earns its place

Sizing a purely solar system for the worst week of the year means overbuilding for the other fifty-one. A common and sensible answer is to size the solar for typical conditions and keep a generator for the rare stretch when it isn't enough. You burn very little fuel, and you avoid paying for a battery bank that sits half-idle most of the year.

Not elegant. Frequently the cheapest correct answer.

Things that catch people out on remote sites

• Security. Panels in an unattended field need fixings that resist theft and a plan for who checks on them.
• Distance and voltage drop. Long cable runs lose voltage. Either size the cable up or move the array closer.
• Dust and livestock. Ground-mounted arrays near animals or dirt roads get filthy and need clearance and fencing.
• Who maintains it. A system an hour down a rough track needs to be simple enough that somebody on site can do the basics.

If you're weighing solar against a line extension quote or a generator, send us the load list and the site details. That comparison is usually straightforward once the numbers are on paper.

Send us the site

Remote sites vary more than houses do, and a quote that isn't based on the actual head, the actual distances and the actual load list isn't worth much.

If you're weighing solar against a line extension quote or another year of hauling fuel, get in touch with the details and we'll give you a straight comparison. Message us, call, or visit the shop in Concordia, Bolinao — bring photos of the site if you have them.