Generators – what does a dairy farm need?

A few years ago when I was working on a dairy farm in Canterbury, New Zealand, we experienced some of the strongest winds ever seen in the country, with gusts exceeding 200km/h in some places. The resulting damage was predictably catastrophic. Thousands of trees fell, causing widespread power outages. Roads were impassable and there was millions of dollars’ worth of damage done to property.

When it came to milking, there were huge complications, as, in many cases, power was not restored for up to eight days. Our farm was one of the lucky ones, as we had access to a generator, although we had to share it with eight other farms.

The daily struggle for access to the generator was manic, as we could only milk whenever it was our turn, so milking time varied radically on a daily basis. Much depended on how quickly the person before us could finish milking.

Hurricane Ophelia brought my New Zealand experience back into focus. This time, I was lucky enough to avoid the eye of the storm and saw very little wreckage; others were not so lucky. The 185km/h winds caused widespread damage, disruption and distress. Dairy farms saw milk sales drop at a significant cost.

In other cases, farmers either weren’t set up properly for a generator or simply couldn’t gain access to one or milk wasn’t cooled properly and had to be dumped.

Simply put, farmers learned that having a back-up power reserve in the form of a generator is essential.

Tractor-powered generators

Tractor-powered generators are the most common type used on Irish farms. The standard tractor PTO-driven generator will invariably be cheaper and because it relies on a tractor it will be assured of running first time during a power outage.

The tractor will have sufficient input power to guarantee stable output from the generator, which is necessary for the starting of milk tank refrigeration compressors and any other units on the farm which start under load. Experts suggest they are probably the best type to use from a farmer point of view, as a tractor is always available with sufficient input power to guarantee stable output from the generator.

A guide for tractor size is KVA x 2 for PTO horsepower (HP); ie, to get the full load out of a 33KVA generator, the tractor should have 66Hp rating at the shaft.

There are two options for PTO-driven generators – a stationary (or bolted down) generator or a generator for the three-point linkage. The farm choice will depend on where power is required. If you potentially need power away from the main yard, then the three-point linkage option is what you will decide on.

Roland Bradley of Bradley PTO Generators, Portlaoise, said: “Three-point linkage generators are not as common, but have some advantages – the main one being that they can be shared between farmers.”

In monetary terms, the other key difference is that VAT is reclaimable on PTO generators which are permanently installed and hard wired – the bolted down generator.

A disadvantage with the PTO-driven generator is that staff do not always set it up correctly. Matching the PTO speed with the required generator speed is crucial. Too slow a PTO speed means the electrical motors will run slow and might not receive the correct voltage, resulting in them drawing more amps and possibly burning out. Running the PTO too fast will have motors working faster and harder than they should.

Most modern generators will come with an automatic voltage regulator and frequency control. This will allow proper operation. It is important that the user follows the manufacturer’s instructions to ensure correct use. PTO generators must be driven at the correct and recommended speed.

When buying a generator, you should invest in quality and a continuous rated set. Continuous power rating is used in applications where supplying power is at a constant 100% load for an unlimited number of hours each year.

Continuous power rated units are most widely used in applications where the power grid is unreachable. Such applications include mining, agriculture or military operations.

Size

Farmers must ensure that their generator is the right size to operate all of their farm equipment, not only milking and cooling, but also working the other farm equipment, such as scrapers, water heaters and water pumps.

Do not buy a generator where it is necessary to turn off certain items during a power cut, as this may lead to burnouts. Farms must update their generators to keep up with the sizes of updated milking and cooling equipment.

A good rule of thumb is for anyone who is on single phase power with a 12-unit parlour or smaller with one compressor and one vacuum pump to get a generator between 25 and 27 kVA.

Anything with two vacuum pumps and two compressors will require a 33 kVA generator or bigger.

Farmers must ensure that their generator is the right size, as the bigger it is, the less trouble it will have supporting the rest of their farm.

This means supporting the milking parlour, the bulk tank and lighting, as well as scrapers water, houses, etc.

Proper installation

It is important that the generator is installed by a registered electrical contractor. The generator and its wiring must also be installed in compliance with all relevant Electro Technical Council of Ireland rules. In order to ensure that parallel operation with the electricity network is not possible, a standby generator must always be connected through a change-over switch.

A standby generator should never be connected on a temporary basis to the electrical circuits in your premises or to your metering point. To do so could endanger you, your neighbours and ESB Networks’ staff.

Lisavaird Co-op initiative

Lisavaird Co-op is one of the small west Cork Co-ops supplying Carbery. With just short of 300 suppliers, it has recently started an initiative to try to get as many of their suppliers kitted out with generators.

Lisavaird expects the majority of suppliers to have a generator by the end of this campaign.

Lisavaird’s Mark O’Brien said: “With our suppliers, we can look at financing options over a one- to two-year period. We have recently placed an order for over 80 generators and the majority of them are for 40 kVA PTO driven generators, with about 50% the bolted-down generators and the rest three-point linkage generators. They are AVR controlled (regulates output) and have an anti-condensation unit which effectively is a small heater to prevent dampness.”

Retail prices for the bolted-down PTO-driven generator (44 kVA) are about €3,500 plus VAT, but the farmer gets the VAT back on these. The price for the three-point linkage generator is about €1,000 more expensive, as you have additional equipment (sockets, trip switches, etc) and of course you don’t get the VAT back on these.

Gas generators

I know of another farmer who recently installed a Briggs & Stratton 14kW automatic gas-powered generator to ensure his property was protected and operational during planned, unplanned and storm-related power cuts. His farm is located away from his family home.

Many times, he wasn’t even aware of the power cut until he got a call from a neighbour that the cows were on the road. Installing the generator on his farm brought reassurance and comfort. During the power cuts in the recent storm, the gas powered generator kicked in automatically without him having to leave the house to switch it on.

I understand the Briggs and Stratton automatic gas-powered generators are available in two sizes, 8kW and 14kW. Powered by Briggs & Stratton Vanguard engines, the generators work off bottled gas (propane) or main gas pipe (natural gas).

Cork generator

Another farmer I know invested in a generator last year, but when he went to turn it on, the generator kicked in for two minutes then died. The issue was the diesel generator hadn’t been started for a long time and dampness was affecting performance. He got it going again, but had to get an electrician to tune it up.