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Insights on how to integrate production, transmission and distribution systems with demand management?

 The topic I am dealing with is finding a way to integrate production, transmission and distribution systems with demand management. Today all the effort devoted to production management and distribution are the dominant ones in the design and construction of national electrical systems. The issue of demand management does not actually affect system design and has a marginal effect on system operation. As a result, the system is built to meet the peaks of daily, annual and multi-year demand, and the result is an inefficient and extremely expensive system. My intention is to develop ways of managing demand so that it can be introduced already at the system design stage and in this way significantly improve the efficiency of the system and the costs of setting it up and operating it. Do you have knowledge on the subject?

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Currently there is an array of design solutions on the demand side that can be applied to reduce the peak capacity (and energy) requirements from the grid. They are generally dealt with under the term DER (distribution energy resources) but can include distributed generation (DG), where customer has a generating resource that can come on line at time of peak and reduce utility's requirement to supply peak capacity, or demand response (DR), where the customer moves part of its demand away from the peak time for the electricity system and brings it back at low system load. Of course both of these solutions will have to be contractual, that is the utility will rely on these measures to be taken by the customer for it to defer its investment on peak capacity. The benefit for the customer being reduced electricity rates because of lower consumption at peak capacity time and the deferring the utility investment in capacity. DR is an easier and less costly solution for the utility as it does not interfere with grid's operations. It just reduces the load on the system at peak and makes it resurface at off peak when capacity is available on the grid's supply and distribution systems. DG is more impactful on the grids in its integration, as it injects power into it. It will increase, for example, short circuit levels at distribution nodes, change the reach of protective relays on distribution feeders, or cause intolerable reverse power flows on system transformers. Hence the need for further investment on the grid components, to be upgraded and become compatible with the new operational mode. It is generally understood that up to 15% DG is tolerable by the grid systems and above that level upgrades will be needed. DG is particularly attractive, economically, if it is used as CHP. That is if heat is also required by the DG host the electricity thus produced is only priced for its portion of fuel consumption (diesel generator with CHP on it). DR has another benefit, for systems with large solar generation in them that will face a fast rising demand level near dusk when the solar goes off, and system night peak is approaching. By removing load through DR the rate of increase in generation will slow down and hence less investment needed on fast ramping generation such as gas turbines. Finally are the new comers in the DER scene such as hybrid solar/battery or wind/battery systems that make the need for capacity provision from the utility significantly reduced. These combinations will need utility as the ultimate capacity provider in cases of long outages in the renewable source generation. In all, there are numerous ways to design the DER systems depending on the load requirements and resource availabilities at the locales and the utility's financial vehicles that incentivizes such systems.

William Buchan's picture
William Buchan on Apr 21, 2021

Afshin, Thank you for the reply.  DER/DG certainly is a way to control demand at peak.  But unfortunately renewable energy - wind and solar - do not contribute during the current peak periods of 4PM to 9PM at night.  Need a renewable solution...Bill Buchan, P.E.

Afshin Matin's picture
Afshin Matin on May 1, 2021

William, I do agree that renewables are not much of help during peak evening period. The DERs also could include distributed generation resources such as diesel gensets and CHPs that can isolate a load section and run on their own power supply for a peak time emergency on the network. So, a bit of flexibility provided to the network and less need for additional operating reserves in the system. This will be for emergency peak support of course and running full time on DER seems a more expensive proposition than grid use (unless you run a CHP). In Canada, we are thinking, with low level solar resources and hydro pretty much utilized, nuclear will be an important addition to support the intermittency of the renewables. Solar will move up as well including farming and residential producers again needing a firm backup in the grid. So, DER could provide cheaper generation in future but with a good firm backup required both for frequency control and the energy itself. It is going to be interesting when it comes to design of all these components working together in a well controlled fashion. Thx.

It is hard to be effective , even in case it is achievable . The integrated power system ( generation , transmission and distribution) looks as The Central Bank of State , while all demands are spot markets of different goods. Does the fluctuations of some good prices affect the CB policies ? 

I believe we manage the grid according to peak load because, in part, we are limited by the technology we have today. To manage against real-time demand, we would probably need:

*  Generation sources that can come line and go offline rapidly.   Natural gas fired turbines cannot do this.   Probably need storage with every generation source to do this. 

*  A rapid communication and management system operated by utilities who would then control all generating sources in a near-instant manner.  This does not exist either.   Nor do the permissions between the utility and the generators.

If we managed to get this far, we would have only managed to address the generation side.  This scenario may also require similar control of the demand side.  But how would we do this when organizations and residents want to draw their electricity instantly, solely at their discretion?....Bill Buchan, P.E., Market Potential, Inc.

EITAN PELED's picture
EITAN PELED on Apr 16, 2021

We are debating this problem and trying to find a solution to it. It is clear to us that large-scale storage systems need to be put in place to meet the changes in demand. With the entry of renewable energy and in order to balance production against demand, large-scale storage facilities are being added to the solar fields. These facilities operate fully in the summer but with the decrease in solar radiation their use decreases until in the winter they are not used at all. But it is precisely in winter that more electricity is needed. We thought it would be right to introduce a management system for managing the solar facilities and in winter to charge them at night when power consumption is low and in the evening to discharge them and thus reduce the need for electricity generation in the evening.
We also thought that these managed facilities could serve as a reserve and replace production facilities used in the city as a reserve with the expansion of the use of renewable energy (wind, solar).

Interesting question!  I think you allude to the fact that you need to plan resources for the full load regardless of DM. if that is the case then DM is a bonus of sorts that brings down customer costs, reduces utility costs, flattens the load curve which means less strain on equipment since you can run more base load units. This process of course lets you get a handle on firm DM that you can plan on and move forward using that portion of DM in the planning process.

This is an area where you can exercise a fair amount of discretion and ingenuity to develop a cohesive plan. In the end though remember that the utility is the load server of last resort so there is an obligation to be there if needed.

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