Is decentralisation the future of sustainable energy?
Decentralisation consists of small plants or even microgenerators that produce power close to its point of use, rather than relying on a central, distributed power grid. This could take the form of an industrial combined heat and power (CHP) plant, where waste products are incinerated onsite, or small, domestic units - such as solar panels or wind turbines attached to individual houses. The shift towards decentralisation can be seen in many industrialised countries. But whether it is sustainable compared with a centrally controlled grid is under debate.
The study concludes that for every advantage that decentralisation offers, there is a disadvantage. For example, distributed generation encourages the development of CHP, which leads to lower fuel consumption. CO2 emissions are also reduced since decentralised plants can only be operated with gas or a similar high-quality fuel with a low carbon content, whereas a large proportion of the centralised plants are coal-fired. However, the construction of many small plants consumes more energy and materials than the construction of a few large plants.
Based on their findings, the authors argue that centralised and distributed generation should be combined in the future. They confirm that decentralisation can help protect the climate, but a combination of technologies need to be used in order to compensate for their individual advantages and disadvantages. For example, solar and wind power offer CO2 savings, but are intermittent. Small gas or oil plants can be used as back up sources of energy, but have higher emissions.
The researchers reached their conclusions by designing four future `energy scenarios` to examine all of the external factors that affect the future development of decentralisation. Each scenario painted a different picture of energy generation in Germany in 2025, and contains a different set of circumstances. Each scenario was designed to reflect the most important variables. For example:
• whether there is a consensus throughout society on the need to protect the environment
• whether government invests heavily in enterprise
• what form the predominant energy supply takes, such as coal, renewables or nuclear
• the distribution of developments (concentrations in urban, suburban or rural areas)
• the contribution of distributed generation to total electricity generation
The team calculated the likely number of decentralised energy plants in Germany, under each scenario. They then developed criteria to score and quantify sustainability, including environmental protection, health protection, security of supply and economic aspects. Each scenario was fully evaluated based on these criteria by 11 scientific experts.
The overall conclusion was that decentralised power generation cannot be rated as clearly better or worse than a central grid. Much depends on other conditions, such as the operating conditions of the decentralised plants or the economic climate.
Security of supply remains controversial, with a number of conflicting influences and great uncertainty. For example, technical grid problems within a small plant have much less severe impacts than failure of a large facility. However, if the decentralised plants are centrally controlled (a so-called `virtual power plant`) then problems with central control may have similar effects to that of failure at a large facility.