21.02.2020

Spotlight on: Combined Heat & Power

In this “Spotlight on…” article, we will find out what Combined Heat & Power is, how it works and in which applications it is mainly used. Next, the benefits of this turbine-based application are discovered before we will learn how it contributes to the EU’s Energy Efficiency Targets.

 1.       Introduction

Sustainable energy production is at the forefront of European energy discussions. One of the key pillars of the EU’s energy policy is to improve energy efficiency by at least 32.5% by 2030 throughout the full energy chain, from production to consumption. One way to do so is to simultaneously produce power and heat to save valuable resources. This is called Combined Heat and Power (CHP) or cogeneration.

 2.       What is Combined Heat and Power?

There are a variety of technologies allowing the simultaneous production of power and heat in one process from a single source of energy. Looking at the turbine technology, CHP means that the heat that would have normally been wasted in the process of power generation in the gas turbine is recovered and used again for heating or cooling in industrial processes or for district heating.

Turbine-based CHP applications can be driven by a wide range of energy sources, such as industrial or agricultural by-products and natural gas. Although less known, heat and power can also be cogenerated using renewable gases, such as hydrogen, when the gas turbine supports these gases (More information about renewable-gas turbines can be found here).

How does turbine-based CHP work?

 As already mentioned above, the principle of CHP constitutes the simultaneous production of power and heat from one single energy source. Gas turbines play a central role in the CHP arrangement. The power generation is guaranteed by a gas turbine driving an electric generator (1) that feeds electricity to the grid (2). The resulting unused heat is not released to the atmosphere but recovered by a Heat Recovery Unit (3). The heat recovery unit then transforms unused heat into steam or hot water, resulting in useful thermal energy (4). 

Figure 1: Combined Heat and Power - How does it work?

Fields of application

One application where this steam can be used is for district heating. Here, the hot steam or water that has been generated while producing electricity is being led (5) through isolated pipes to a city district in order to heat buildings. It is also noteworthy that the water is reused again and not wasted. One can say that using CHP for district heating is a way of producing electricity while heating districts. This application can primarily be found in Northern European countries.

  

Cogeneration can be also found in a variety of industrial processes and sectors, especially in sectors that need a lot of heat (chemical industry, iron, steel, paper, cement and aluminium production). Because industrial processes of these sectors are so energy-intensive, the application of CHP is not only sustainable, but also cost-saving.

Figure 2: District heating

 3.       What are the benefits of CHP?

Efficient: Guaranteeing a high degree of energy efficiency, CHP applications can be seen as the solution for the challenges related to the EU’s energy policy. Their innovative design allows CHP applications to produce with the same amount of fuel both heat and power instead of power alone. Consequently, CHP applications can reach energy efficiency levels of up to 90% (European Commission, 2014, can be found here), which is the key benefit of cogeneration.

Figure 3: CHP Energy Efficiency. Values from http://www.coenergycanada.ca/chp/

Reliable: Another important benefit of cogeneration is that CHP plants operating with gas or biomass are not dependent on external factors, such as weather conditions, and are able to deliver in a stable and reliable way.

Sustainable: As improved energy efficiency is the key benefit from cogeneration, one can clearly state that less fuel is needed than for separate power and heat generation. Indeed, COGEN Europe estimates that cogeneration in industry is saving Europe around 15 million tons of oil equivalent (Toe) (COGEN Europe, 2012) causing less emissions. This way, the environmental impact of power and heat generation decreases tremendously.

4.       CHP helps reaching European energy efficiency targets

Since its 2012 Energy Efficiency Directive, the European Commission places high priority on energy efficiency. Indeed, amended in 2018, the directive lays out energy efficiency targets for 2030 of at least 32.5% compared to 2007. The European Commission identifies cogeneration as key tool to increase its energy efficiency levels and to consequently reach the 2030 targets. In its publication “Good Practice in energy efficiency” from 2017, the European Commission states that many projects related to waste heat recovery are being funded and advisory groups are being implemented for developing efficient district heating and cooling infrastructure across Europe.

This political support for cogeneration increases the importance of gas turbines for the future energy system. Indeed, as gas turbines constitute one of the central elements of CHP plants, they can and should be seen as key enabler for achieving Europe’s energy efficiency targets. In combination with renewable gases, CHP has the potential to power and heat the European Union and to reach a carbon-neutral economy by 2050. 

Download the article here.