Commercial pig unit electricity monitoring project
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The Farmex/BPEX Energy project was a small scale pilot project to measure electricity use at a practical level over a range of uses. Readings from a total of 84 meters were recorded every 15 minutes over a period of 1 to 2 years on 11 different farms. Circuits measured covered a range of uses from power used by ACNV systems through to total use of farrowing rooms.
Whilst the measurements cover a spectrum of farms, a range of use, and varying styles of production, the numbers are too small, and the variation within them so great, that they should not be considered typical, average or representative as such. Averages are of farms in the study, and the figures may well differ markedly from averages of the industry.
Production Stages
Data has been notionally divided into Farrowing, Nursery and Growers on a notional “per pig produced” basis. For comparison, 4 weeks farrowing, 6 weeks nursery and 10 weeks grower has been assumed in the charts shown here, but there are actually wide differences between farms.
This chart shows a general estimate of energy use on the farms studied. It shows averaged figures for each stage of production, expressed as kWh (“units”) per pig produced. However, it is an average of a wide range of situations – for example ACNV buildings are included. Hence, the overall totals may not correspond with uses for individual purposes.
Overall, some reduction was achieved during project (after discounting differences such as changes in measured population and seasonal effects).
Heating
Farrowing heating – mostly creep heating - represents a large proportion of total electricity use, and is the dominant energy use in farrowing rooms. Heating use appears substantially higher now than earlier studies would suggest. This is partly due to the wide use of “back lamps” (uncontrolled heat lamps around farrowing time). There was no difference between users with heat lamps and those with heat pads, nor between higher and lower creep lamp ratings. Those with lower lamp power, or heat pads, tended to use higher levels more of the time, negating the difference. The average cost is around £2.50 per farrowing place per week at current prices.
Creep heating represents a significant opportunity for energy saving. With an initial electricity use of £2.40 per week, one of the farms made some minor changes to creep design (adding curtains) and settings, and achieved a saving of 80 pence per crate per week, whilst improving weaning weights. However, other producers seem reluctant to follow the example.
Weaner room heating use (as shown here) is deceptive. Whilst it is relatively close to the theoretical requirement (around 1 kWh per pig), it is unrepresentative of the industry as a whole, and of these producers at the start of the project. At the outset, all producers studied used far more, mostly because of high or very high minimum ventilation settings. Most users appeared relatively unaware of the impact of minimum ventilation settings on heating use. Better use of weaner heating represents an “easy win”, but producers appear to need the demonstration of electricity measurement.
Ventilation
Some farms have ACNV systems, where electricity consumption is almost negligible; most of the power use in ACNV systems is for controllers. The inclusion of ACNV buildings in the total Units per Pig skews the overall figures. Calculated only on rooms with fan ventilation, average cost per pig is around 11 units for ventilation, but this is strongly seasonal.
Fan ventilation cost in farrowing rooms and, for the most part weaner rooms also, is a small part of total energy use – using ACNV in these rooms offers little clear benefit, and fan efficiency as such is a very minor issue.
The main factors affecting fan electricity use are stocking (pig heat to be removed) and temperature differential. Temperature differential is a result of outside temperature and target inside temperature. Outside temperature is beyond the control of users, but target temperature is; lowering set temperatures increases power use considerably, especially in mild weather. The third factor is ventilation capacity. In warm weather, lower capacity systems “limit out” more readily. This “caps” electricity use, but results in higher room temperatures for more of the time.
There was little evidence – on the farms studied – that electrical efficiency of fans was a major factor in grower electricity consumption. Since fans vary comparatively little in their energy use per unit of ventilation, power use is an effective way of measuring ventilation rate, and should be considered as a technique for detecting ventilation failure (rather than mains failure only).
Lighting
Lighting was a significant revelation, having been very little studied at a practical farm level (despite the existence of both UK and EC regulations). Electricity monitoring is revealed to be a very effective way of measuring lighting duration and level.
In almost all cases, lighting was manually switched according to convenience or working practices on the farm. Relation to pig needs appears vague or absent. On one farm, for example, main lights are not switched on at weekends, as no one is working in the afternoon to switch them off. Producers appear reluctant to automate lighting – few have timers, and tend to by bypassed even if present. Mistakes such as forgetting to turn lights off at night account for around 30% of lighting consumption in some cases.
The legal requirement for a minimum of 8 hours is generally ignored, as is the required period of dark in many cases. Most users left some lighting on at all times in fan buildings though, curiously, none did in ACNV buildings (even with fan and ACNV buildings on the same farm). As well as using less power for ventilation, ACNV buildings use less power for lighting. Surprisingly, there is little change in lighting electricity use summer to winter, even in buildings with some levels of natural light.
Comparison of lighting period (by electricity) with other measurements (such as water intake and activity levels as measured by thermal balance) showed that lighting can have a significant impact on behaviour and body clock, though not in the simple “light response” as shown in poultry. For example, pigs have a longer “day” – and therefore lower peak levels of water consumption and body heat output – in the early summer than in late winter.
Feed Systems
Only a few feed systems were monitored. Ad lib dry feed systems use little energy. Costs are around 0.02 to 0.06 pence per pig per week – less than 1/10th a kWh per pig through the growing stage. At this level, it is almost beneath mention and energy efficiency almost immaterial. However, electricity monitoring does prove to be an excellent way of checking that the system is working consistently.
For wet feed systems, though, consumption was varying and inconsistent. The three systems monitored gave estimated costs of around 5 pence, 11 pence and 49 pence per pig respectively (grower stage) – around 0.6 to 6 units per pig. This is a large range. The higher value may be an over-estimate (it is not clear how many pigs it feeds), and it is possible the highest value may be due to incorrect allocation to the number of pigs but, at a cost of around £4,500 a year, is a significant part of the electricity bill. In one of the systems (11 pence per pig), energy consumption was clearly related to the quantity of feed delivered. The other two, however, used almost the same all the time, whether feed was consumed or not. This suggests that the system design could be improved to reduce energy consumption.
General Points
At the outset of the project, the somewhat simple view was taken that it was just a matter of measuring electricity on a range of typical farms. It would then be possible to quantify – more precisely – the impact of this or that energy saving measure, and make recommendations that could be adopted by the industry on a cost-benefit basis.
In practice, the variation between one farm and another, even if they appear similar, is far too large – or perhaps the sample of farms here is too small – for this to be meaningful in terms of equipment or external factors.
Energy use is only very generally, and to a limited extent, related to the physical needs of the required tasks. This is evident to some degree in weaner heating and grower ventilation, but less so with things like creep heating and lighting.
The biggest factor, by far, is what the users choose to do with the equipment and buildings. For example, the “energy efficient” farm with farrowing rooms with ACNV, natural lighting and 125 watt lamps using more than the farm with fan ventilation, artificial lighting and 250 watt lamps. That’s because the first farm chooses to have the lamps full on all the time, instead of varying according to the age of piglets. Another farm, with heat pads, uses less – but only because it shares one pad between two litters. One farm may leave weaner room lights on all the time, while another may switch them on and off. One farm aims to keep growers at 20ºC, while another prefers 16ºC – and will use far more electricity even if had more efficient fans.
One might expect that these differences in modes of use are based on some kind of notional cost-benefit on behalf of the users in their particular circumstances. Either that higher cost gives some identifiable benefit, or that they have found that avoiding the cost incurs penalties such as ill health.
If so, it is at best a very loose relationship, if we can judge from weaner heating. Farms had high weaner heating bills because of high minimum ventilation rates, apparently through a belief in the health benefits of doing so. However, having reduced minimum ventilation, none appear to have changed back – making one question whether a health benefit exists. Similar situations clearly pertain with farrowing heating and grower ventilation – within the project we have measured the costs, but benefit of higher electricity use is difficult to determine. In one specific example, costs were reduced but productivity was improved.
It is tempting to suggest that the answer lies in better training, but this is true only in so far as the answers are known – or at least commonly agreed. Within the study, the two biggest costs are creep heating (plus back lamps) and grower fan ventilation. However, there is no particular agreement whether mortality, growth rates and health are better in temperature controlled creep enclosures or open creeps. Nor yet is there any consensus view whether growers are better kept at 16, 18, 20 or even 22ºC. These are both crucial to determining costs and clearly have more impact than equipment or methods.
The only thing that can be clearly said is that effective energy saving – energy saving with a positive, or at least no negative, effect on productivity – seems far more likely if producers take an active approach to it.
Feedback – measurement of electricity consumption and keeping a close eye on impact – is crucial. Passive methods such as buying creep controls, heat pads, more efficient fans or even having better insulation – simply “having the right things – do not in themselves produce energy efficiency. Most of the farrowing rooms monitored had temperature controls, but many were full on the whole time because of the way they are set. Insulation, even in weaner rooms where it is often held to have a major impact on heating cost, was a minor factor compared to control settings.
ACNV is a major energy saver in grower/finisher accommodation both for fans and lighting, but the question of whether not production – growth rates, feed conversion, mortality or even welfare – has been little examined.
Page last updated 08 June 2010