Challenges in distributed generation 1

[jellyhut]

Hello All,

I am looking to understand the reasons why distributed energy resources do not yet make up a significant portion of generation. The idea has obvious benefits (more reliable system, decreased losses, etc.) and the installation of renewable resources is encouraged by many utilities and civic bodies; yet it does not seem to have taken off in most areas. What are some of the barriers or challenges associated with installing distributed generation systems? And do you think that their prevalence is likely to increase in the future, or will they continue to make up a relatively small portion of generation?

Thank you!

 

[xnuke]

This is a huge topic. I teach a college course on grid integration of renewables, and we're only able to scratch the surface of all of the issues. Do an internet search and pick one to discuss per thread. Also, this (or any other thread along these lines) probably belongs in a more apropos forum - maybe Energy engineering general discussion, or Where is Engineering Going in the Next 5 Years.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[DTR2011]

One quick example is that (in the USA for example) many of our MV distribution lines are largely radial systems with simple phase and ground overcurrent relaying. To add DG to these lines, much more complex protection schemes are required for the DG and the connecting utility. There are major safety issues for the linemen and general public if the DG is not tripped off for a fault on the line.

I have seen requirements for small DG to interconnect to MV lines which require distance relaying, in addition to IEEE 1547 requirements. Unless the DG has some huge $$$ incentives, it is not often financially feasible for small scale. As a recent example, a 850 kW cow manure digester plant was over $1M for the plant alone. A dedicated feeder to the substation was $200k. Don't exactly know what the additional PT's and relaying on utility side was. The only real winner there was the farmer.

 

[dpc]

As xnuke says, it is a combination of factors, but the primary underlying issue is simple economics and economy of scale. In addition, every type of energy source has its own set of additional problems and concerns. Promoters of alternative energy sources generally vastly understate the infrastructure modifications required to incorporate it into the grid, including switching, metering, monitoring, protection, and ssfety-related issues. Many of these folks are simple ignorant of the technical issues, but others know better, but choose to downplay the problems because they are trying to make money from it.

Also, I don't necessarily accept your "obvious benefits", especially regarding reliability.

I remain skeptical that distributed generation will play anything more than a secondary role in overall power production until there are major technology breakthroughs that allow cheap storage of generated energy and cheap transmission of bulk power. I don't see either on the horizon. The only exception might be PV systems, but even those will be quite limited in terms of the total energy requirements for the grid.