Those who study or are interested in the subject of Renewable Energy (RE) may have come across all these acronyms one time or another. They may also know the extent to which these terms are applied interchangeably, in research as well as in practice. If it was not just for the ambiguity of philosophical terms like sustainability, we have gotten ourselves confused about what someone means when they say Distributed Generation (DG): do they mean systems that employ Renewable Energy Technologies (RET) at the scale of distribution networks or do they simply also mean conventional energy technologies at that scale? When people say DES: is it D for decentralized or D for distributed ? Also, what’s the difference between D Energy Systems and D Energy Resource ?
While most of the communications that employ these terms, mainly journal articles, are clear enough for their readers to comprehend the connotations attached (as they are usually clarified in the beginning of the article), it would be useful to clarify these terms in general as well.
Here’s a very informal attempt to impart some clarity. Please note that this is by no means absolute or given and is liable to change as the scientific community arrives (hopefully) at a system of meanings that proffers further connotational quality.
Renewable Energy (RE): A form of energy whose rate of resource replenishment is greater than the rate of utilization it can ever be subjected to.
Renewable Energy Technology(ies) (RET): Technologies — material or physical artifacts — that harness RE.
Renewable Energy Systems (RES): Systems — inclusive of the material (RET) and immaterial (institutions) — that refer to alternate forms of energy production, distribution and consumption.
Decentralized Energy Resource (DER): Energy resources that are locally available and harnessable by technologies. Here, scale is important. An oil well used locally without connections to the global markets can be considered as a decentralized energy resource, albeit conventional. Similarly, given their nature, RE like solar, wind and biomass, are classified as DERs because harnessing them through large scale centralized power plants (like Ivanpah or PS10) doesn’t take away from their being utilized at smaller decentralized scales.
Decentralized Energy Systems (DES): The system of energy production, distribution and consumption that outlines the alternative ecosystem of technologies, institutions, along with their enabling actors. This is better understood when contrasted with Centralized Energy Systems (CES) which are based on central production with consumers situated at the end of supply lines. Contrastingly, DES is the constellation of different techno-institutional configurations like DG, Microgrids, Smart Microgrids and Smart Grids.
Distributed Generation (DG): Energy production at the scale of distribution networks. It can be conventional or renewable depending on the technologies being used to harness energy, but typically taken to mean Distributed Renewable Energy Generation.
Microgrids (MG): Local systems of energy production, distribution and consumption that are semi-centralized through aggregation of DG locally, and having a switchable connection to the main grid.
Smart Microgrids (SMG): Microgrids with an additional layer of technical functionality through ICT (information and communication technologies) like smart metering or advanced metering infrastructure (AMI), and smart sensing and automated switching technologies.
Smart Grids (SG): Large-scale counterparts of SMG. These are national, regional or utility grid-level implementations of ICT over existing electricity grid infrastructure or/as well as aggregation of SMG eventually leading to a system of microgrids all tied together to form the main grid. As such, microgrids are building blocks of smart grids.
The definitions can be developed further and are obviously subject to change as technology and its use changes overtime.
Let me know if I had missed any acronyms or if you’d have articulated any of these differently.
Have a great week ahead!!