Solar power in our future

We have talked about PV solar power here many times. I have lived off-grid as have at least two other NL members so we know it works. What's relatively new, at least in this region, is grid-tie PV systems. Some are commercial, others are home systems. What generally is getting in the way of more of these systems are laws (that benefit big-scale power producers).

An opinion piece titled Reader Supported News looks at how this is changing, and why.

As the price of solar panels drops, they increasingly are being spontaneously bought and installed by villagers throughout the world, who are often ill-served, or not served at all, by the central power grid in their countries. Some remain off the grid once they have gone solar. Just as many countries in Africa skipped the stage of building copper wire telephone transmission lines all over the place, and instead went straight for cell phones, so they may also be able to avoid trying to deliver power through a central grid to everyone.

One of this examples is the recently installed power plant in Guatemala.

Central America’s largest solar facility, in Guatamala, is still relatively small by world standards (5 megawatts). But it will power 24,000 homes and in a country like Guatamala, that is huge.

Guatemala has a law in place which allows any electricity consumer to sell energy back to the utility. The electricity charge on your bill is for the net usage for the month. That is, your total consumption minus what you produced and fed back into the grid. With low prices of PV panels and synchronous inverters, producing at least some of your power is very practical. With such a law in Nicaragua, moving toward all-renewable power becomes easier.

For you doubters, peak electricity demand occurs during peak sun hours. Thus, adding PV-solar to the mix is very effective.

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Interesting solution

A co-worker and his neighbour came up with this system for their remote cottages. They are now trying to sell them locally here. I think it is a very simple and elegant design and it works loke a charm. Brad is currently running everything in his cottage (usual amenities) except a stove.

Looks right

For off-grid, it sounds like a reasonable package. I lived off-grid with a bigger but similar system with no problems. (I had about 2000W of panels, 8 - 6V, 450Ah batteries and a 3500W inverter.)

I am working on the web page for what we are doing which will include a comparison of off-grid vs. synchronous inverter systems. If you have access to a relatively reliable grid, the synchronous inverter approach can offer a much cheaper system. For example, besides eliminating the need for batteries, the charge controller is eliminated. Not an option for everyone, of course.

A Very Good Deal

for wealthy Guatemalans who can afford a large PV system.

The problem with this model is, it doesn't fund the infrastructure (grids, distribution stations, and cost of the management of the system).

It may appeal to populist instincts, but in truth, there is no free lunch. Someone has to pay these costs. Rates can be structured to where the smallest consumers pay little or nothing, but with this arrangement, the very wealthy will pay nothing beyond the capital investment of their plant. They simply have to generate sufficient excess power to cover their usage during off-peak hours.

Who then pays the rest of the costs of the system?

Clearly, the availability of the clean power is a good thing. And, the cost of a KWH at the margin (beyond what the wealthy Guatelateco can use) is very low. But, like much of the rest of the socialist model, it's not sustainable. It depends on the "capital fairy". If the utility is permitted to purchase the power for somewhat less than they return it for, then they have the capital (from the profit, another socialist dirty word)-- to continue to maintain and extend the grid.

As a short term solution, to encourage the development of solar power, it might have merit. A kind of "affirmative action" for the solar panel industry, if you will. As a long term arrangement, it's simply not sustainable.

Who pays for it now?

"Infrastructure, grids, distribution stations, and cost of the management of the system"

Its paid for by the likes of Blue Energy making electricity by windmills, selling the power to the distributors at an agreed rate who in turn sell it for more, to you, also at an agreed rate.

So same deal for the buy back from consumer system. Nobody has said what that Guatamalan buy back rate is. But I doubt it's 1:1 is it or?

Actually, it is

Money doesn't enter into the deal until they go to compute your monthly bill. I said something like "electricity cost" which is not your total bill. Effectively, the meter runs backwards with what you produce, up to a maximum of what you used. Then, the electricity cost is based on the difference. (If the difference is negative, you just did the utility a favor -- this charge cannot be negative).

Now, in addition to "consumo energia" there is:

  • cargo fijo mensual -- basically the cost of you having the connection
  • servicio alumbrado publico -- street lights which is a fixed cost rather than a consumption cost

At current rates, even with zero consumption, this gets you a bill of almost $7.

I bet most people agree

we have the right to generate our own alternative power even though that reduces the utility company sales and profits.
A terrific idea to reduce the almost $.40/KWH cost on my factura & I am surprised that more commercial companies here do not do that to reduce their daytime cost. Even if it does not involve "running the meter backwards."
I fact, where are the entrepreneurs that could be installing grid-tie PV systems at a business and charging them reduced rates as an alternative to an equipment sale?

Disnorte-Dissur now has the proven capability to supply power needs of the country but we will see what happens now now that Hugo is not supplying the oil.
A claim that they can increase profits buying at retail and reselling at the same price is a new accounting concept - That says that they are losing money buying at wholesale and selling at retail because of distribution costs.
That also says that they ought to be happy to pay the customer every month to generate excess power if the total meter charge does go negative to increase their profits even more.
If so, why are they even in the energy business?
Theft is a big problem - As users generate their own alternate power that cost will be spread among fewer customers and their rates will have to go up to pay. Same for distribution infrastructure maintenance & improvements.

Old school math and accounting says that someone has to pay for the cost of storing customer excess PV daytime power so that that the customer can use it at night. Buying high & selling high at the same price does not cut it.
The utility does not eat that cost - The other customers pay.

$500 For A System

with a grid tie inverter?


I don't have said system in place yet but:

  • 285W PV solar panel (From Florida) -- $162 (a pallet of panels on the way)
  • 300W grid-tie inverter (from China) ~$100 (There are various sources but I have no firm deal with anyone yet.)

I figure $100 for duty and shipping (clearly not for a single unit but if combined) and $50 for "accessories".

A full-sun day should give you at least the equivalent of six hours of maximum power so that's 285W * 6 hours * 30 days = 51,300Wh.

More data

In my inverter shopping the $100 figure for a ~300W inverter seems to be about right but I am finding fair-sized synchronous inverters in the $400-500 range. They are 2-3kW units. I have seen 100kW, 3-phase units as well for ~$13,000.

Note that unlike your typical system with batteries, you don't need:

  • An inverter that can meet your peak demand
  • A "charge controller" as you are not charging anything. The synchronous inverter deals with converting the variable voltage from the panels into 120 or 240VAC.

One other question I got asked was "what about backup power if the grid goes down". I have two answers:

  • If you are talking about during the day interruptions, there are units that generate a fake grid signal. Basically you switch off your grid connection (completely -- such that your house is isolated) and then inject this signal which the inverter will sync with. Then you have as much power as the PV array is producing for local use.
  • A UPS "upgrade". In general, this is what I would recommend. If the grid goes away there are some limited things you really need to operate. For example, a computer (me) or TV (futbol fan). Adding a bigger battery to a regular UPS is probably the most practical solution.

I disagree

(which, of course, won't surprise you). First, let's talk about "wealthy Guatemalans" which of course can apply to any semi-large power user.

Electric rates in Guatemala (just like in Nicaragua) are graduated. That is, low-level users pay a much lower rate than the high-level users. The rate structure exists for various reasons but the end result is that if you are a high consumer then it is more cost-effective for you to reduce your net consumption. It becomes less practical to try to get to net zero but very practical to get to, say, below 50kWh/month. Talking to typical folk it seems easy to use that much electricity even in a small family house.

On the PV system costs end, you can add a system capable of producing around 50kWh/month at a relatively low cost. With careful buying practices, you can buy the complete system for around $500. It is likely that cooperatives would be willing to loan money for such a purchase.

Now, your second question, "Who then pays the rest of the costs of the system?". While the utility company marketing folks ask this all the time (and then give you the wrong answer), it is quite simple. Locally-produced power, generally available during peak load times, reduces infrastructure costs.

  • If peak loads are reduced, required peak generating capacity is reduced. As generation to meet peak loads tends to be the most costly to operate and most polluting, reducing peak load is a big benefit to the utilities.
  • Generation locally at peak load times reduces grid costs in two ways. First, the peak capacity of the grid is reduced. Second, power produced closer to where it is consumed reduces grid losses thus reducing distribution costs.

Note that I have been doing a lot of homework on this because I am working on a project that will take advantage of local generation with the grid acting as a battery. It will reduce costs and pollution. I plan to try to get the law changed in Nicaragua so that this same approach will work in Nicaragua as well.

held off for a long time..

finally broke down last month and we put a solar pannal up at the farm..have to be able to charge cell phones..and watch movies