Making the best of energy in your dairy

With such large, diverse demands, the dairy industry is ideally placed to take advantage of combined heat and power (CHP) technology, and use it to improve process profitability.

Not only does it provide an efficient way of delivering cooling energy to meet chilling and refrigeration requirements, but it also generates electricity to power other processes while capturing any heat that would otherwise go to waste. 

Nigel Thompson, sales manager – Gas Power Solutions at Finning UK & Ireland (Finning), a provider of both natural gas and biogas CHP technologies, discusses these benefits in more detail.

The power of CHP

If the sight of clouds of hot steam billowing from the top of power plants has ever struck you as inefficient, CHP might be the ideal technology for you.

A CHP system consists of an internal combustion engine or gas turbine to provide motive power, an electrical generator and a means of recovering heat from the exhaust gas stream.

The engine/turbine runs the generator in the same way that large, conventional plants produce power but rather than simply releasing the exhaust gases to the atmosphere it makes use of them, extracting the heat that would normally be wasted.

A standard power-only generator is typically only 40% fuel-efficient, with all the potential thermal energy produced going to waste. But because a CHP system captures and makes use of this heat, their fuel efficiency can increase to more than 75%, and in some cases as much as 88%.

Therefore, for the same amount of fuel, almost twice as much useful energy is generated.

Hot and cold

Beyond this, there’s the opportunity presented by trigeneration. Though a plant’s exact energy requirements will vary depending on dozens of factors, one of the biggest drains on power in a dairy plant is almost always going to be its electrical cooling system.

Indeed, refrigeration systems in UK dairy processing plants use an estimated 250 GWh of power each year, so any technology that can help improve energy efficiency in this area should be welcomed.

Trigeneration uses an absorption chiller to convert the captured heat into cooling energy. This is economical and environmentally-friendly, as it eliminates harmful refrigerants and reduces overall air emissions.

Less wear and tear

An added bonus is that as absorption chillers have no moving parts, there’s much less opportunity for wear and tear, resulting in minimal maintenance costs. Additionally, there are now chillers available on the market that can be powered directly with the CHP exhaust, completely removing the need for an intermediate exhaust gas heat exchanger.

The exact savings that trigeneration could potentially deliver for a dairy plant is extremely variable – a site audit can help to give an indication of how big they might be. However, it is estimated that around 66% of the energy required to produce butter is consumed by cooling systems, and 20% for cheese and fluid milk.

As a result, there are certainly opportunities for dairy plants to reduce costs and improve operational efficiencies with this technology.

Milking the benefits

Even the production of conventional fluid milk consumes around 0.95 MMBtu for each tonne of product, with cheese requiring almost four times as much. Processes such as spray drying powdered milk and condensing milk are also particularly energy-intensive, with products such as raw milk needing to be chilled throughout.

With demands varying so much from site to site, it’s vitally important to make sure a CHP system is sized correctly. As a general rule, the bigger a plant is the more efficient it is, which means that ideally it will be powerful enough to meet the day-to-day demands of the dairy. However, it’s also important to avoid making the plant too big, as any heat that can’t be used gets wasted and drags down the system’s overall efficiency.

In most cases Finning recommends calculating a plant’s base electrical load profile, as this takes into account any fluctuations in electrical consumption throughout a day.

Payback in as little as three years

Another way to ensure that a CHP system is running as efficiently as possible is to sign an operations and maintenance (O&M) contract at the same time as installation. Regular servicing and support will ensure that you have years of high-quality service.

Finning offers not only practical advice and guidance on specifying and installing the right CHP unit for a site’s requirements, but also provides an O&M contract to ensure efficiencies are delivered as promised.

With a payback period of as little as three years, CHP represents an excellent opportunity for cost-conscious dairy manufacturers considering how to power their processes. If operators in the dairy industry take advantage of CHP and all it has to offer, significant cost savings and energy efficiencies can be realised, helping plants to maximise profitability and maintain productivity levels.

As far as energy solutions go, CHP is cream of the crop.

Finning has prepared a downloadable guide, offering further detail on the benefits of CHP for dairy manufacturers. Visit www.finning.co.uk/chp/dairy.