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A Rotten Apple a Day: a Microgeneration Story – Part 1

As someone who was born in 1984, I was told the future would be all about #computers and #renewable energies. That meant for me a world full of #solar roofs and a bounty of computer games. Very few could predict the way the internet has changed our life, and it is as equally hard to envision what it will be like when billions of people will be energy producers.


This series of articles aims to serve as an introduction to microgeneration and smart grids for a non-technical audience. These are concepts we feel it is increasingly important to grasp to make educated choices when we buy energy related products or choose a service provider. 

Let’s start this journey with some definitions. Microgeneration refers to decentralized, small-scale systems that generate local power and/or heat. When several of these systems are linked together in a grid, for instance in the case of group of houses or flats, a need to optimize the energy flow emerges: smart grids use computers to manage these complex systems. 

One might ask, why would we need microgeneration and smart grids? 

To answer this, we need to take a step back. In 2010, the EU launched a plan, known as Europe 2020 strategy, committed to tackling climate change. Three of the main proposals are: 

  • to reduce #greenhouse gases emission by 20% compared to 1990

  • to increase energy efficiency by 20%

  • to reach 20% of renewable energy consumption.

The struggle to reduce #carbon emissions is paying its dividends, and it is very likely Europe will meet the target: despite economic growth of 58%, a 22% reduction was achieved in 2017.

The introduction of building #automation systems, #modulating #controls and #drives has surely played a huge role in achieving such a goal. Nonetheless, when looking at the total energy consumption by energy products, we also notice that the rise of renewable energies and gas, along with the fall of coal and oil products, has played a significant role in tackling GHG emissions. 

Because renewables are so effective in fighting climate change, the energy world is undergoing a transformation to further increase consumption of these products, made possible by advances in technology and profound changes in the energy market over the last few decades. Microgeneration is a one of the ways the energy sector is changing.

By its nature, microgeneration is strongly intertwined with the residential sector. Hence, before digging deeper into the subject, we should get familiar with a few figures. The numbers provided here describe the European energy market, and therefore might not reflect your country’s energy consumption. However, broadly speaking, the same principles apply: 

  • the energy demand for the #residential sector accounts for one quarter of all energy consumed in EU;

  • almost 80% of the demand is for heating of space and water: half of the energy comes from gas, whilst 30% of the remaining half is covered by renewables;

  • conversely, electricity used for lighting and most electrical appliances only represents 13.8 % of the energy consumed by households. 

It is also worth noting that the overall gas demand is not evenly spread across the EU, but is most significant among the largest energy consumers: the Netherlands, Germany, Italy and the UK. 

In these countries, given the widespread use of gas appliances and the existence of a reliable gas network, further GHG reductions could be achieved by introducing a new culture of producing electricity directly in our homes when burning gas for heating purposes. This is done by swapping our conventional boilers for #micro #cogenerators, the domestic equivalent of industrial power plants. Also known as micro combined heat and power (mCHP), residential cogeneration is our first example of microgeneration. 

To explain why using these new boilers can lead to #GHG reductions, let’s look at their industrial counterpart, a more mature and established technology, as often in the engineering world, to innovate is to apply the same principles in different contexts. 

In a centralized system, power is produced in large plants. Converting the energy stored in fuel into electricity is very inefficient, and waste heat is usually twice the power produced. It makes sense to recover this energy, which would be otherwise released in the #atmosphere by means of cooling towers, as unfortunately often happens. Where heat recovery takes place, it can drive a variety of thermal processes: pulp and paper mills, steel mills, food and chemical processing plants. This is the reason why large industrial sites are usually located near power plants or develop their own on-site generation.

#District #heating schemes follow the same approach, though instead of being used in industrial processes, excess heat is diverted to serve buildings. However, district heating has limited application as we don’t usually live near power stations. This also means that the electricity we use must travel great distances to reach our homes, which adds more energy losses. On the heating side, although our domestic boilers have improved considerably, they too produce waste heat. Therefore, we can see that the conventional way to supply heat and power to households is very inefficient. 

Although micro cogenerators are also inefficient in turning fuel into electricity (actually more inefficient than conventional power plants), because they operate in our homes we can use almost all the waste heat for heating space and water. It is also worth noting that these boilers produce electricity and heat in a ratio that meets household demands. 

Why don’t we all have a micro cogenerator in our houses then? The answer to this question has its roots in the history of the deregulated energy market, which is the topic for the next blog. In the following articles, we will also look at some microgeneration systems available in 2019; and study in more detail how conventional boilers and micro cogenerators work. Furthermore, we’ll see how much gas can be extracted from food waste; report on our testing of a Stirling Engine mCHP unit with biogas; and much more!

Written by Marco Fanasca


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