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Question

Are you studying production of local energy within the city vs. large utility energy farms?

DIANA SWIDLER's picture
education UPENN

Sustainability professional with an international profile and working experience in a variety of professional settings. Specialized in renewable energy, above all solar energy, and green...

  • Member since 2021
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I am helping a nonprofit build a case in front of the Public Utility Commission to produce solar energy locally rather than produce it outside the city. Solar energy from a utility-scale solar farm is cheaper per kWh. Still, when we include the transmission and distribution costs associated with upgrading the grid, localized solar energy production becomes more cost-effective. We want to prove that solar panels covering parking lots can represent not only a supply of reliable and local energy but an additional profit for the landowner. I was wondering if there is anyone out there studying already this comparative?

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Diana, In my consulting experience I have found local solar can be competitive with centralized solar, but it depends quite on the rate structure in the state you are in.  Rates and associated charges vary widely from state to state.  With respect to T&D charges, these charges are most often treated as a shared charge for all that use the grid.  So unless the solar plans you have include storage and islanding(e.g. a community microgrid), you will likely have a difficult time omitting these charges.  For your presentation to the PUC, you are probably better focusing on:

*  The efficient use of local generated solar, because a lot of energy is lost through old T&D lines

*  Subsequent GHG benefit

 *  Resiliency

Your argument gets stronger if you include storage.  It'll be stronger yet with islanding.

Good Luck...Bill Buchan, P.E., Market Potential, Inc.

Yes - I've been involved in a host of different types of projects, many at the distribution/customer level.this means projects such as micro grids, DER, DPPs (distributed platform providers) etc. Customer owned generation with aggregators and storage in localized areas. In some areas this is becoming the only choice as HV ROWS are becoming harder to find. There is not a one size fits all but I think you need to recognize where customer generation is going to develop on its own and start from there. I like the idea of DER but question the likelihood that DPP will become  a widespread thing.

I am a mechanical engineer and have been involved in the engineering and construction of power plants.  I spent 10 years with Florida Power Corporation....now called Duke Energy.  These questions deal more with electricity, power flow, resistance, etc.  

That being said, let me state some of the limited facts that I know from my utility days at FPC.

FPC, which is a fully vertically integrated electric utility company, which means: generation, transmission, and distribution. 10% of the generator output was consumed by the utility itself, for station service, transmission, and distribution losses. Many people thank that there is a big loss in transmission, and that is not true.  As I recall, station service is around 6% to 7% of the total loss, meaning 3% to 4% is the line loss.

For a distribution company these percentages are different in that small cities are distribution only.

Here in Florida, the electric system is about 50% load factor and is primarily driven by residential load.  This translates to a big load during the day because of air conditioning, with a smaller load at night.  Years ago, I learned that northern utilities had more of an 80% load factor due to industrial, commercial, and 24 / 7 heating requirements.

Now with this info, let's return to your initial question. You are correct in that remotely located, utility-scale solar panels will require a grid upgrade to move the large megawatts of power from the many acre solar farm to the small residential user. Solar panels located on houses, parking garages, buildings, etc., can simply be plugged into the existing distribution system (assuming that the panels are sized within the existing service drop and won't overload the wires serving the area). For instance, my home has a 240 volt single phase 200 amp service drop.  Therefore, I could install a 48,000 watt solar array on my roof.  However, there are two problems.  One, my roof is too small to accomodate the square footage required to support that size of solar array.   Second, the electric utility assumes diversity in a residential neighborhood.  Meaning that, except for Thanksgiving, not all homes will be operating a 12,000 watt oven, a 4,500 watt water heater, a 10,000 watt heat strip, a 4,000 watt air conditioner and etc.  This diversity allows for smaller distribution wires in the neighborhood, while code requires that my electric panel and service drop must be able to handle all loads being on at the same time. 

A distribution substation has many feeders that go out into the city or neighborhood.  These feeders are typically 12,000 volt 3-phase and can handle 5 to 10 megawatts of power.  Feeders are further broken down into their component parts of varying sizes, locations, etc. 

As seen from this feeder view, one can not install a single 5 or 10 megawatt solar array unless you are close to the substation and can connect at 12,000 volts 3-phase.  One could install hundreds of 1,000 watt solar panels on hundreds of houses.

I hope this provides a backbone for others to build on. 

In my consulting experience, localized power production is very cost effective when the comparison (with centralized) is made in terms of back up power also. 

One real life example. Having an onsite power generation that produces during the on-peak hours (at a lower than the grid cost) and for the grid's unplanned power interruptions this becomes an attractive alternative!

This onsite power maybe battery storage, solar or even traditional diesel gensets. 

Solar Power World has couple of interviews with John Frederick of Poly Tex Solar, and Apadana Solar based in Minnesota.

Also Art O'Donnell currently on a DOE fellowship with the New Mexico Public Regulation Commission, is researching this exact question.

https://www.solarpowerworldonline.com/2019/10/apadana-solar-poly-tex-complete-1-3-mw-solar-carport-in-minneapolis/

Diana, yes I do think to localize solar is a good idea however what I found during my studies is that there are several challenges to overcome. I think the biggest challenge is the storage of additional energy generated needs to go somewhere when not needed. That's where we need the national grit, to store it into the grit. But when it's needed again the cusumers must buy it back for use. Many feel its unfair because it's energy that they produced and supplied for free. Than there is still the burning issues of environmental impacts. Many has claimed so far that solar energy have little to non effect on our environment and causing no harm to the planet, animals and humans. What I found is that it's not quite accurate because after the expiration dates of all the equipment it needs recycling. As we know solar panels is the biggest problem due to the silica it contains. Now my thinking is that say you have a community of 1000 households and each having say 4 panels for generation. Once it reach their expiring dates it must be replaced. The home owner get a company or supplier to do so. That company replace it and then have to get rid of the old ones. Where and how do they expose of it? It all ends up in bins than taken to dumpsites where they mostly landfill it or it's just dumped on a pile. Now that's is a problem towards environmental impact. Toxic products that's exposed to the air we breath.

 

In order to minimize the solar waste I found that building a steam engine driven by infused technology could be the answer to many of the problems we face globally. 

DIANA SWIDLER's picture
DIANA SWIDLER on Apr 14, 2021

Hi Jacques, 

Thanks for your input. First, I would love to know more about the steam engine. The recycling of solar panels is definitely an issue that we have to consider and include in a solar panel's life cycle emissions and find ways to reduce its environmental impact or even eliminate it. 

Secondly, you are completely right about the problem of the energy excedent. California is wasting solar energy right now because they don't know what to do with it. This is why they invest in battery storage, so energy can be stored during the day and then used during the night when there is no sun and electricity prices are higher. In our study, we include the use of V2G (vehicles to grid) to balance out the intermittency of solar power. Imagine that you can charge your EV during working hours, then drive back home and use your vehicle battery as a power backup for your home.

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