Cost saving energy audits

Business analysts say that reducing costs should be the number one tactic for companies in tough economic times. Quarrying is an energy intensive sector, with energy making up as much as 21 percent of total cost of supplies (excluding labour). Any savings that can be made on energy costs go straight to improving the bottom line.  By SIMON WILKINSON.

A new project has been started recently by the Aggregate and Quarry Association (AQA) to help members reduce their energy costs and improve performance.  The project has been developed in partnership with the Energy Efficiency and Conservation Authority (EECA).

This AQA ‘best practice energy programme’ is providing a practical way for aggregate and quarry companies to drive down their energy costs by offering half-price energy audits, delivered by high quality auditors with experience in the sector.

For a relatively small initial investment in an energy audit, companies have been finding savings averaging more than 10 percent of their energy costs and some quarrying operations have found potential energy savings of as much as 20 percent of their total annual energy spend. 

An energy audit involves a fully qualified and experienced energy auditor visiting a site to review how and where energy is being used in a company’s operations. The auditors then look for practical opportunities to improve the efficiency of the plant and associated services. In some cases onsite vehicles are also examined to look for opportunities to improve fuel efficiency.

An energy audit of a South Island quarry operation found that the quarry was being heavily penalised by ‘congestion period demand’ charges. The auditors recommended installing a warning system to enable load reduction during these periods. Loads could be reduced during these times by using material stockpiles while some machinery is switched off.

 Installing a timed alarm connected to a ripple relay to enable this peak load shedding will cost the company $1500 for potential annual savings of $10,721.

Another recent energy audit of a quarry found that two pumps supplying water to a process water reservoir were working too hard and supplying water at such a high rate it was overflowing the reservoir and flowing to a sump requiring further pumping. This meant the water was being unnecessarily pumped twice. The auditor’s solution was to install a VSD on one pump together with a PID level control system that utilises an ultrasonic level sensor in the reservoir. This will speed regulate the pump motor as required to maintain a constant level in the tank. Implementing the whole system cost $30,000 leading to savings of $25,300 in energy costs every year, giving a simple payback of 1.2 years. 

EECA has recently published a case study of Winstone Aggregates’ review of the efficiency of its vehicle fleet. By implementing some simple changes such as reducing idling times, covering loaded and unloaded trucks, installing speed limiters and improving tyre management the company is on track to save 10 percent of its annual fuel bill (there’s a link to this case study on the EECA website).

In addition to co-ordinating half price energy audits for members, the best practice energy programme is working on other ways to help the quarrying industry adopt energy efficient practices, including benchmarking and industry training. 

The programme has started investigated the potential usefulness of a tool that will enable operators to benchmark their energy performance against other companies. By examining a quarry’s energy use per tonne of material produced it is possible to identify poor performance and the need to review efficiency. 

There is a wide range of material produced by the industry and it is clear that the amount of energy used depends on the finished product and the level of processing involved. Any benchmarking tool developed for the industry would need to compare apples-with-apples by having appropriate benchmarks for different materials or processes.  This is something the AQA programme is working on.

Training of industry operatives is also a good way to help quarry companies to address energy efficiency. By integrating energy efficiency into industry training it may be possible to help quarry staff continuously look for energy efficiency opportunities and ensure that energy efficiency is business-as-usual. 

The AQA wants the Best Practice Energy Programme to be as useful and relevant to member companies as possible.  The AQA would welcome the feedback of operators on what they would like to see as part of the programme that would really help to implement efficiency gains. 

If you have any ideas, or would like to find out more about the Best Practice Energy Programme you can contact the AQA programme coordinators: Simon Wilkinson 021 944992 or Ket Bradshaw 021 369495.