Image credit:Electric Power Systems Research 57 (2001) 195-204; Ackermann et. al.
My recent claim of 'distributed power' being inherently superior created some controversy. As did my claim that distributed power was a more useful and important concept than 'green power,' per se. (See: Decision Time: Invest In Distributed, Versus Central Power & More High Voltage Transmission Lines?) A wind turbine in the back yard or solar panel on the roof are mostly what get cited as examples of distributed power. There is a much richer field of technical possibilities, however (as indicated in the above figure). Before getting into the several advantages of distributed power - including both renewable and non-renewable generation technologies - I thought it would be good to review what constitutes distributed power.Synonyms for "distributed power" unfortunately sound like terms sociologists and demographers might use. As pointed out by Ackermann, Andersson, & Soder in their paper Distributed generation: a definition: "...Anglo-American countries often use the term 'embedded generation', North American countries the term 'dispersed generation', and in Europe and parts of Asia, the term 'decentralised generation' is applied for the same type of generation."
Some common and easily agreed-upon characteristics of 'distributed power.'
Most would agree that a distributed power source is either connected on the customer side of the meter, or to the local distribution network, or can switch to both; but not to a transmission network.
Although a distributed power source may range from kilowatts to megawatts, it's power is not centrally dispatched. (A utility does not primarily control it; although, I wonder if 'smart meters' will challenge that assumption.)
The intricacies of power grid connections are what makes it difficult to come up with a simple definition. Ackermann et al offer some examples which illustrate this issue, (I am paraphrasing here):
- A Combined Heat & Power (CHP) system is located on a large industrial site and the industrial customer is directly connected to the transmission network. In this case, the CHP system can be described as distributed generation as it is connected on the customer side of the meter.
- A medium-sized wind farm is directly connected to the transmission system, due to the capacity limit of the local distribution network. In this case, the wind farm cannot be described as distributed generation.
- The produced energy of a wind farm is almost totally used within its own network; however, during nights with very low demand and high wind speeds, the wind farm actually exports energy back into the transmission system [which would make it only half compliant with common definitions].
Earlier posts on distributed power.
Duke Power Investing In Distributed Solar Generation Scheme
Pyramid Power Goes Green In San Francisco California :
Distributed Energy Stock Index (DESI)
The Jellyfish Wind Appliance: Plug-In Wind Power for $400
SchwarmStrom In Your Basement - How German Is It? :
Big Coal Gets Wired: With A Little Help From Its Friends :
Beating the Energy Efficiency Paradox (Part II)