As I mentioned in my last post, I am trying to reduce the energy usage at work by looking at the process equipment. The first piece(s) of equipment to fall under the spotlight was the compressor. Although maintenance did not want to change any of the settings they did arrange for someone from the Company who installed and services the compressors to come in and talk to me about them (although maintenance were conspicuously absent from the meeting).
The outcome of the meeting was that we had a set of dataloggers installed to look at the air usage over a week. From that we received a report detailing the loads during the week, the cost of generating the air, the annual cost of the air, and a number of recommendations for saving energy and money. It is hoped that when faced with the hard data, then maintenance and management would decide that changes needed to be made.
The first of the recommendations was to use only one compressor, not only would this save us electricity costs in excess of £1000 per year, but would also save £250 a year in servicing costs. This might not have been an economically viable option if it wasn’t for the fact that the pipework is already in place and all we have to do it turn a valve on. So, from this, another question arises – why do we have a separate compressor? The second plant was installed in 2001, 15 years after the first plant – why not use the same compressor? There is no one in the Company that can answer this question – so, as maintenance cannot think of a good reason not to do this, the valve will be opened and both plants monitored to check that there is no problem. The specification of the main compressor and the air requirements of the main plant are such that it can easily provide enough air for both plants. Money saved.
Second recommendation? You’ve guessed it, turn the pressure down – apparently a one bar reduction in pressure will save £185 per year. You might think that this is not much of a saving, but at 10p per kWh, it is equivalent to 1 tonne of CO2e per year, and it is all waste. I was a little disappointed that the survey could not tell me what my minimum operating pressure is, but as far as I can tell, as long as I keep above 6bar, then the second plant will be fine, and if I do reduce the pressure below the minimum for the main plant then it will just stop – which is not a disaster, we just turn the pressure back up and start it up again – as long as it is in a controlled way no damage will be done.
Recommendation three was something I am not sure about – there is the possibility of recovering the heat generated by the compressor and using it to heat the warehouse. However, the figures were based on the cost of electrical heating, gas is about 20% of the cost of electricity at the moment, and we do not want heat all year round. This suggestion is parked for now.
The final suggestion is to conduct a leak survey. Whilst we do check for leaks on a weekly basis, this is only done by listening for any leaks. It is possible that this is missed, and, if we are using the connecting pipework across the warehouse to power both plants it may be more worthwhile (expected cost £350). However, what is making me think that this could be worthwhile is that the survey showed the air usage graphically for the week. There were a couple of days where the main plant was shut down, and the air usage, whilst low, was not zero. Whilst there may be something that is kept under pressure when the plant is off, in which case maybe we can lock it off, it may be because of leaks in the system. I have estimated that if this was the case, then the cost of these leaks is £300 per annum.
So, I have the data, and although it cost £200 to get the survey done, we should be able to save up to £1500 a year for no outlay at all and we can have the changes made by the start of the CRCEE.