Dry cooling in Boar stations – return on investment 2 years

Inno+ is a specialist in pre conditioning incoming air for Pig and Poultry stables. Our aim is to achieve an optimal climate for the animals all year round. In the winter period, incoming air is preheated with energy recovered from air washers and transported to air inlet exchangers before entering the room. For the summer, we have developed a new concept specifically for the cooling of boar, sow and finisher buildings. The last 2 summers in the Netherlands have had a high impact on pig production through heat stress. With our understanding of the negative effect traditional ‘wet’ cooling systems can have, we have developed a cooling concept to really solve the summer problems. This ‘air conditioning’ system not only cools but also dehumidifies incoming air, with the outside temperature always cooled to 17°C and the humidity remaining in the comfort zone of below 60%. What this means, in countries like the Netherlands where summer temperatures rise above 17°C for over 2000 hours per year. We can reduce the loss in piglet production by maintaining a quality of air for the sows to live in comfortably. This comfort means they reproduce better.

So how does it work?

Cold water of 10°C is produced with an air to water cooling machine and is then sent via a piping system to heat exchangers that cool the incoming air. Unlike traditional wet cooling systems where the air makes contact with the water it travels through. This system provides a ‘dry’ interface in the form of dense piping that has cold water running through it. This means there is no moisture transfer to the incoming air, infact the air contact with the cold pipes has the effect of condensing moisture in the air and in effect stripping it out. This means the air flowing into the building has less moisture in it and therefore less energy content or Enthalpy. In regions where the Enthalpy of the outside air is constantly high, this can have a massive benefit. Removing any air energy means the animals are not challenged when trying to transfer their heat energy into air that in principle is already full of energy.

Massive benefit for semen production

This is particularly interesting for Boar semen production, where the air volumes we need to manage are smaller, but the returns in terms of quality semen production and benefits for improved farrowing are massive. Hopefully explaining how we calculate the requirements to achieve ‘optimal air’ will clarify why doing it this way is so important. The real culprit at the end of the day is air energy, frequently ignored when wet cooling is used.

Cool calculation

So how do we calculate the amount of cooling required for a group of pigs? Well first, you will require some basic information about the climate you expect to manage. For instance, the amount of air required for the animals concerned. You will also need to have a good idea about the quality of the air that the system will have to deal with. A climate that produces air with high energy or enthalpy will require more cooling than one where the air energy content is lower.

How much air?

One of the first things to think about is how much air you will need to condition. Most closed house systems will have already worked this out when designing the climate system. This is typically the amount of air required per pig at peak time, multiplied by the number of pigs.

By way of example – 50 boars in Myanmar

ventilation rate with cooling of the incoming air: 200 m3/hour/boar
Total max. ventilation: 50 x 200 = 10,000 m3/hour

Peaking off

The next thing to do is determine for what length of time the air outside needs to be treated. This calculation also requires a bit of inbuilt reasoning as to what the ‘peak’ is. To avoid false economy it does not always make sense to design the system to the max enthalpy. If for instance the peak is only for a short period that will not have a dramatic impact on production, then it makes sense to design the system to handle an enthalpy ‘up to’ a point where impact can be reduced.

In some countries, this could be 10% of the total number of days required, but in others may be less than 4%. The key to designing an efficient dry cooling system is to have a good feeling about how local climate can affect air quality and what is the workable range beyond the ´optimal zone´ that the animals can remain in comfort. At the end of the day, the science is simple, but the system designer does need to have good knowledge of climate and animal production.

For the sake of the example below, we have used a max 100kj/kg as the value to take off peak, on the assumption that the few hours a year when the enthalpy is above this will not have a significant impact on production.

Region Myanmar

Enthalpy for the region: 107 kJ/kg
Peaking off at: 100 kJ/kg
Cooling to target: 17°C/100% RH (47,8 kJ/kg)

This means we design a system to 100kJ/kg not 107kj/kg, which leaves few hours where the system is not running at optimal. The judgement is based on whether this period above the comfort zone could reach critical point. For example, the RH moves above 75% having a significant impact on the animals. Whilst the natural desire is to invest in a system that handles 100% cooling needs, the extra cost will probably lead us to a position of compromise. At the end of the day, the system still has to pay back.

Therefore Cooling hours:

Cooling hours (>17°C/100%RH): 7900 hours
Hours between 47,8 kJ and 100 kJ: 7880 hours
Hours above 100 KJ/kg: 20 hours

Calculating the energy required to cool 1000m3 down by 52,2kj/kg as an average

100 kJ/kg – 47, 8 kJ/kg = 52, 2 kJ/kg which we have to cool (extract energy)
Then using the table below to determine how much installed cooling capacity is required to cool 1000m3/h of air. 17, 4 kW. The actual calculation being, amount of air x the density x gap in enthalpy we need to bridge. Then convert from kj/s to kW (/3600 seconds)

‘1000m3 x 1.21kg/m3 x 52,2kj/kg / 3600 secs = 17,4kW/h’

Calculate the total amount of energy required for the given air volume

It is then quite easy to calculate how much energy would be required at peaked off enthalpy to deliver cooling to the target enthalpy.

For a max. 100 kJ/kg enthalpy for 50 boars @ 200m3/h

200 x 200 m3/hour = 10,000 m3/hour
10,000 / 1.000 = 10
10 x 17,4 = 174 kW

We therefore need a system that delivers 174kW of cooling capacity.

Installed Cooling capacity per 1.000 m3/hour ventilation rate (chiller capacity)

Enthalpy Outside condition [kJ/kg]	Design point enthalpy incoming air [kJ/kg]	Installed Cooling capacity per 1.000 m³/hour ventilation rate in [kW]
100	47,8 (=17˚C / 100% RH)	17,4
95	47,8 (=17˚C / 100% RH)	15,8
90	47,8 (=17˚C / 100% RH)	14,1
85	47,8 (=17˚C / 100% RH)	12,4
80	47,8 (=17˚C / 100% RH)	10,7
75	47,8 (=17˚C / 100% RH)	9,1
70	47,8 (=17˚C / 100% RH)	7,4
65	47,8 (=17˚C / 100% RH)	5,7
60	47,8 (=17˚C / 100% RH)	4,1
55	47,8 (=17˚C / 100% RH)	2,4

Knowing we require 2,7kW cooling power per kW of electricity (EER – energy efficiency rate); we can work out how much electricity is required to provide cooling during this hot period of 7880 hours.

Energy needed per year

Average enthalpy for cooling hours – 73,2 kj/kg
This means 9,1kw/2.7 = 3,48kW/h for 1000m3 (see below)
Or 37,58kW for 10,800m3/h (54 boars x 200m3/h)
37, 58 x 7678 hours = 288,539 kW electricity per year.
@0,07 euros/kW = 20,367 euros per year

Does it work?

An example of a recent project quoted in Myanmar region for – 50 boars

Lost doses due to heat stress in Myanmar

Heat stress affects semen production by a loss of 30 doses/boar per month.
54 boars x 30 doses x 10.6 months = 17,172 doses.
Profit per dose for the boar farmer is up to 1 Euro per dose
This means between up to 17,172 euros lost over a 10.6 month period for 50 boars.

The other benefit is the removal of the aerosol effect by dry cooling and the reduction in spread of bacteria that effects quality of sperm. (No figures on this yet).

Impact of poor semen through heat stress leads to 5% drop in farrowing (various factors).

A typical boar stud is around 54 boars

1 boar typically services 150 sows per year.
This means 54 boars/8,100 sows.
Assuming 1 sow produces 25 piglets (?)/year, that’s 202,500 piglets
Based on current Dutch prices 50 euros with a profit margin of around 15 euros.
202,500 x 15 euros x 5% = 151,875 euros profit lost/year.
Assume – 10,6 months this could mean – 134,156 euros
Add profitability of semen – up to 17,172 euros

Potential benefit per year – 151,328 euros

If we take into account cost of the system and running costs, we would expect a payback of between 2-3 years.

The combination of this cooling solution with solar panels is ideal. At times in the summer when there is a peak in the production of solar energy, there is also a peak in the energy absorbed by the chiller. The energy costs of the chiller are then eliminated by the company’s own production of energy.

Good cooling essential in pig production

Cooling is becoming more and more an essential part of good pig production. In addition to a direct economic benefit, in terms of more piglets produced per sow and lower boar and sow mortality. There is also a general interest regarding animal welfare and wellbeing. Certainly not forgetting, the welfare of the people working in the stables under extreme warm uncomfortable conditions.

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