Standby for money generation

How often have you seen a standby generator sitting in a dusty corner and wondered how many times it has actually run? The answer is normally just a few hundred hours, and it is not unusual for even 40-year-old sets to have run for only 300 to 400 hours.

In many cases, this is a wasted asset. It could have been routinely earning money if its owner had specified it differently, and if the electricity company had been approached for a different tariff.

Electricity companies like base load. It is constant, easy to plan and makes the most efficient use of their infrastructure.

But in the real world, electricity demand depends on many factors, such as the time of year, the time of day, the weather, which day of the week it is and even whether it is half-time in the cup final.

Given that no-one wants a loss of supply, the generation and supply equipment is sized to take the resulting peaks into account.

Typically, nuclear and coal-fired power stations are used for base load, while smaller, more flexible stations make up some of the shortfall.

Expensive pump-storage systems meet the very short-term spikes.

Managing the supply to meet the demand is, however, only one option. The alternative is to manage the demand that the grid sees.

The good news is that supply companies will reward you for capping your maximum demand by setting you a different tariff, but could extend the benefits further by encouraging the export of electricity to the National Grid at premium rates during these times.

Peak prospects

So, what does this all mean as far as your own generator set is concerned? Having decided that capping demand is an efficient use of the generator, you need to decide how to achieve this without causing disruption to your own organisation. No-one will thank you if they have to go without electricity for an hour or more.

The answer is to plug this gap with your own generating capability. Although this is more expensive to operate than buying power normally, when you offset this against the savings of a better tariff, you will show a net saving.

In addition, you will ensure that your standby generator is kept in good order and has been regularly tested – many are not. Using your generator to cap imported electricity is called ‘peak lopping’ or ‘peak shaving’.

You will ensure your standby generator is kept in good order and is regularly tested – many are not

You can also become part of the National Grid reserve service and sell electricity to the grid. This is when the National Grid requests that you start your generator to reduce the load on the network.

Meeting the need

So how do you go about making the most of these opportunities?

In its most basic form, a standby generator has a manual changeover switch to connect either the generator or the mains supply to your load, with no option to run the generator in parallel.

More often, however, the system to start the generator and connect the load to it is automated. It may also have a means of synchronising and returning the load to the mains, once the power has been restored.

To run the generator in parallel or to export electricity you will need to specify a slightly more complex control system that has additional protections in place.

You will also need to specify a prime-rated generator set rather than a standby set and talk to the electricity company about different tariffs.

No limits

The main difference between a prime-rated generator set and a standby one is that the prime-rated set is rated to run an unlimited number of hours per year at 70% load factor. A standby-rated set is rated to run a maximum of 500 hours per year.

If you are considering supplying a reserve service, you must also consider how to start the set. Some suppliers, such as Finning, offer a 24-hour monitoring facility, which can manage the engine operation remotely.

All of the above does add to the cost, typically by between 10% and 25%, depending on the base specification, if considered before purchase. You will find, however, that it does pay to do your maths, especially with the cost of electricity rising.

After all, you will be transforming a piece of underused capital infrastructure into a revenue stream – surely every facilities manager’s dream.