Understanding cogeneration and trigeneration

For any organisation seeking reduced operating costs and improved power efficiency, as well as a reduction in carbon emissions, a number of new technologies will likely be on the table.

It's important too, as according to Energy efficiency: A compelling global resource, a study from McKinsey Sustainability & Resource Productivity, energy efficiency accounts for around 40 per cent of greenhouse gas reduction potential that can be realised at a relatively low cost.

Combined systems are perhaps one of the better options, however, offering a level of cost reduction and efficiency that's difficult to match. In order to clear up any confusion surrounding the two major combined systems, it's time to take a closer look at how cogeneration and trigeneration actually work.


Also known as combined heat and power (CHP), cogeneration takes the production of usable heat and power and integrates them into a single process. The end result? A system that generates electricity, but also captures the waste heat and uses it as useful energy. It's certainly a far more efficient solution than the current method of energy generation, where waste heat is simply blown away in the wind out of massive chimney stacks.

Siemens explained that through a well-designed cogeneration scheme, users can expect a conversion efficiency of up to 95 per cent. Cogeneration is an excellent option for cutting down on emissions and improving power reliability.

How it works:

As this solution involves generating electrical and thermal energy from the same fuel source, the need for additional heating systems is effectively eliminated. Instead, electricity is generated through a gas turbine generator and the waste heat from the turbine exhaust is recovered using a heat exchanger. This heat can be used to generate either steam or hot water.

The solutions available:

Optimal Group has a number of solutions available under the Capstone Generator range, with different fuel options also on offer. For example, the C65 & C65 ICHP MicroTurbine – Natural Gas unit is one of the smaller options available, which ensures it can be installed even in tight locations. 

The C200 MicroTurbine – Liquid Fuels unit, on the other hand, is significantly larger and suited to installations on larger sites. Of course, there are also a number of other micro turbines available.


Given the name similarity, cogeneration and trigeneration may often be confused as one and the same. However, trigeneration actually differs significantly. These systems use similar CHP units, but bring in an absorption chiller so there's an option to provide cooling alongside the electricity and heat. It's certainly a more versatile option if cooling is required.

Organisations may want to consider trigeneration if there are buildings onsite with continuous or seasonal cooling demands. So how do trigeneration systems work?

How it works:

The units begin with a traditional cogeneration plan, coupled with the aforementioned absorption refrigeration system. The hot water from the cooling circuit of the cogeneration plant acts as drive energy for the chiller unit. As the gas turbine also continues to pump out hot exhaust, this can be used as an energy source.

Organisations using trigeneration systems can realise conversion efficiency similar to that of a cogeneration system, and potentially even greater. With cooling factored in, there's a good chance of easily cutting out another expense during the hotter months.

The solutions available:

As with cogeneration, Optimal Group offers a number of trigeneration systems fit for the demands of a modern organisation. The C200 MicroTurbine – Liquid Fuels, is a unit capable of ultra-low emissions and tens of millions of operating hours. This isn't to mention the simplicity. Unlike more complicated power security systems, this unit features just one moving part.

When more power is required, the C800 HP Power Package – Natural Gas is fit for the task. This is actually the world's largest air-bearing micro turbine, producing 800 kilowatts of clean energy. It's able to operate with little need for maintenance and has a high electrical efficiency over a wide operating range. An internal fuel gas compressor is also available for low fuel pressure natural gas applications.

Considering power security

With both cogeneration and trigeneration, there's one other benefit that could sway an organisation to take advantage of the systems: greater power security. Both systems use micro turbines powered by either natural gas of liquid fuels, meaning there's no dependence on grid electricity.

In the event of a power cut, the organisation can switch over solely to the cogeneration or trigeneration system, which in turn ensures there's a reduced risk of being without power while the grid is repaired. 

With energy efficiency and reduced operating costs ranking high in the operational agenda of many organisations, there's no better time to assess the merits of cogeneration and trigeneration. To learn more about the solutions available for these processes, reach out to Optimal Group today.