Further to our previous blog, a diverse “multi-path” approach is required for energy management to reduce energy, greenhouse gas emissions and operating costs.  Two of the paths previously suggested include comparing energy efficiency between diverse premises (building power signatures) and the five-steps to successful energy management.  This discussion continues with power bench marking  to help in reducing energy costs.  Remember “What gets measured, gets done”.

Load Factor (LF): Is a measure or indication of the extent to which the electricity supply is fully utilised i.e. the higher the better, up to 100%.  It is a measure of the volatility in the premise’s electrical load, with regards to its electrical peaks and valleys.  Typical monthly LF in Queensland:

• Single shift factory: 20% to 30%
• Office buildings: 30% to 40%
• University: 50% to 60%
• Large hospital: 60% to 75%

Power Factor (PF): Is a measure of how effectively premises are using their electricity.  A poor PF will add to a premise’s energy costs and waste energy i.e. preferably above 0.95 and closer to 1 the better. 

Improving PF will reduce the need to spend additional funds on increasing the capacity of the network, thereby minimising electricity price increases.  Premises on kVA tariffs are especially vulnerable to kVA demand charges. It is imperative whenever cost-effective, to improve the PF at time of maximum demand.

Improving PF, reduces the amount of current flowing in the electricity network, thereby reducing the network losses and consequently reducing greenhouse gas emissions.  For example a PF of 0.5 requires 100% (twice as much) more current to handle the same load.  The answer to these efficiencies is to reduce the reactive power drawn from the network by improving the customer’s PF.  PF was discussed in a previous blog.

Off-Peak Ratio: Is a measure of how much electricity is consumed out-of-hours i.e. the lower the better, down to 0%.  Large industrial premises consume around 40% electricity during off-peak times.  Typical off-peak hours in Queensland are between 10pm to 7am (overnight) each weekday and all weekends.

Energy index (EI) & Demand index (DI): Tracking changes in the overall energy consumption of a premise without accounting for the underlying activity levels of that premise gives no indication of the relative efficiency of energy use.  The EI indicator provides a measure of how annual energy consumption (kWh or MJ) is related to activity levels, such as gross building area, nett lettable area, equivalent full-time employee, or production variable.  The lower the EI, the better.

The Demand index (DI) is a measure like EI but includes only the electrical maximum or peak demand in kilowatts (kW) or kilovolt amp (kVA).  The lower the DI, the better.

Please contact Susmet to assess proper bench marking across your sites, from our range of experience.

Disclaimer:

This blog is part of a continuing series discussing sustainability and energy management issues. Contributions featuring achievements, techniques, products, and processes are welcome. Please feel free to contact Susmet to suggest ideas on future issues.

Whilst every effort is made to see that no inaccurate or misleading data, opinion or statement appears in this blog, Susmet accepts no responsibility or liability whatsoever for the consequences of any such inaccurate or misleading data, opinion, or statement.