Solar Installation in McGregor, Texas August 2024 Start

tahanson43206 · 2024-08-12 08:41:46

This topic is dedicated to news about and comments upon a solar power installation scheduled for a rural location near McGregor, Texas, in August of 2024.

Construction began this morning on our solar PV installation.
GW

If photographs or other documentation become available this topic is a good place for them.

(th)

tahanson43206 · 2024-08-12 08:42:35

This post is reserved for an index to posts that may be contributed by NewMars members over time:

1) Post #1 announcement of project start

Update 2024/08/24 - kbd512 provides an overview of solar installations in this post: http://newmars.com/forums/viewtopic.php … 33#p226033

(th)

Last edited by tahanson43206 (2024-08-24 19:02:59)

SpaceNut · 2024-08-12 18:41:29

Much has been learned from kbd512 solar offset efforts to combat the rising household energy bill.
Currently I am looking to see if I can get ahold of the solar panel brand being used to see if I can get around the dim or shaded light issue and over voltage outputs to a charging power wall issue.

tahanson43206 · 2024-08-12 20:29:37

While we wait for news directly from GW, I can report (by email) that the installation of all panels was completed in one day, at both the house and a second building where a tenant rents space for a work shop. The technicians will be back tomorrow to install electronics and perform system checkout.

Details of pricing may differ a bit from the system reported by kbd512. One detail that caught my eye is that the power delivered to the grid pays half what that same power costs when it is pulled ** from ** the grid.

GW is hoping to put about 70% of the solar power into the grid from the house, and 100% of the power from the shop. I assume that must mean the tenant pays his own electric bill, but perhaps GW will clarify that point.

(th)

GW Johnson · 2024-08-13 15:21:45

Solar installation is completed and operational. There are two systems hooked to two separate electric meters from Heart of Texas Electric Cooperative. One is on the house (some 21 panels), and one is on my shop, a separate meter, some 8 panels. Each has its own inverter to make AC phased to the grid, and its own cutoff switch and breaker. The panels themselves are roughly 2-something feet by 4-something ft, probably about a square meter each.

The reason these things do not supply power during a grid outage is that the inverter controls require AC from the grid to function at all. When the grid is down, the solar is down. There is no way around that, as long as the house current is AC. The electricians showed me where to hook in the back up generators for grid outages, and they tell me such generators are a better deal than battery backups. I need to save up, and have a back up generator installed on the house. My renter (on the shop meter) already has a small one. We'll probably hook him up first.

My renter is paying rent, but doesn't use much electricity. I don't charge him for that directly, just an allowance in the rent. He built his own home out of shipping containers, which is very well insulated and located in the shade under a metal roof. It has a very efficient heat pump for heating and air conditioning.

Those 8 panels on the shop are designed to average about 100% of the electricity use on the shop meter. Those on the house about 70-75% of the electricity use on the house meter (we have about 2200 sq.ft under air conditioning). On a hot sunny afternoon like this, both meters are running rapidly backwards. We are generating more than we use, and selling the excess back to the co-op. We are part of the distributed generating system they are trying to add to their system.

This system cost a tad over $49K to install. We expect a tad over $14K as the tax rebate for it. That makes its effective cost about $35K. It should effectively zero the shop electricity bill except for the meter fee. It should effectively reduce the house electricity bill to the meter fee plus a little bit of usage, on average. It is warrantied for 25 years, with an expected lifetime in excess of 40 years. The inverters communicate by wifi with the company; if something goes wrong, they send the technicians right out.

It's nearly 4:30 in the afternoon here as I type, and if you go outside, the sun beating down still feels like a hammer blow, unless you wear a broad-brimmed hat. That's just central-to-west Texas in the summertime. About 80 F at dawn, about 100-105 F near 4 to 5 PM. Typical August conditions.

GW

SpaceNut · 2024-08-13 19:13:50

Solar Panel kWh Calculator: kWh Production Per Day, Month, Year

https://www.ctec.coop/energy-efficiency/solar/

Five Texas Electric Coops Sign Collective Solar Power Purchase Agreement

tahanson43206 · 2024-08-14 06:06:09

Per email from GW Johnson, he has not yet begun the process of deciding what capacity generator he might need/want to install to keep the solar system running in case of a grid outage. My experience is with a 3 KW Honda and a 14 Kw Kohler. The Honda had a self starter which was nice, but I still had to connect a cable from the 240 VAC outlet to a port into the house. The Kohler did all that automatically, which is even better.

I'm hoping GW might be willing to report performance data on the solar installation from time to time. This forum would be enhanced by Real Universe data from members, to supplement the steady supply derived from Internet sources.

(th)

GW Johnson · 2024-08-15 09:25:21

There's no routine reports coming from this. The tale will be told by the monthly bills, over the course of a year from this point.

I can get a subjective impression by watching meters run backward. But that's not data. And in a sunny August day in Texas, making lots of solar electricity is to be expected.

GW

SpaceNut · 2024-08-16 16:08:38

Go solar and lock in lower energy costs with ReVision.

Eversource Net Metering Frequently Asked Questions

While you pay for the energy at one rate in my case 22 cent a kw but that only lasts up to a cap for the month before you get charge at an even higher rate.
The net return for the kw going back to the grid is in some case at a lesser value of about 9 cent a kw that you give back.

Some of it is due to deregulation as the company that owns the wire is part of the selling of energy to the consumer.

What To Consider Before Installing A New Home Battery

SpaceNut · 2024-08-18 12:02:55

Powering Your Home: The Ultimate Guide to Solar Solutions

To finance or the old fashion method of saving until it can be bought.

Finance fees versus inflation.

One could finance the grid tie, disconnect and a few other pieces from saving and add a panel as you can afford them to the overall system wattage desired. Getting the energy as you go.

GW Johnson · 2024-08-23 08:19:10

The co-op came out and set a new meter on the house. The display shows when the meter is running backwards, like the over at my shop.

I went and looked: it was a bright sunny morning with the sun about halfway up to zenith. With the air conditioner running, the meter was stull moving backward, just very slowly. With it not running, the meter was moving very fast backwards. I don't think the hot water heater was running (it's an all-electric house out in the country). No lights on, just a couple of computers and maybe the TV. The house system uses 21 panels, feeding DC to one inverter that feeds phased AC at that meter.

The one over at the shop was running backwards pretty fast, even with my renter's air conditioner running. Hs domicile is much smaller and better shaded and insulated than my house. The shop system uses 8 panels feeding DC to one inverter that feeds phased AC at that shop meter.

How's that for a performance report? We were selling electricity back to grid from both systems, even with air conditioners running in a serious heat wave. The high that day, about 4 hours later, was about 105F. It was already 95F when watched the meters that morning.

The system went operational August 13. The bills for August show up in September. I expect to see lower bills for August, half of which the meters ran backwards significantly. I expect dramatically lower bills for the month of September, which will show up in October.

GW

Last edited by GW Johnson (2024-08-23 08:19:25)

SpaceNut · 2024-08-24 10:53:40

It sounds great...
Can GW or KBD512 tell me more about the grid tie device and cutout switch that are required in addition to the new meter.

18 Misunderstood Facts About Solar Power and Home Economics

Others say that there are just 14 Common Myths About Solar Power

So are the thin film flexible in the offering for use?
What To Know About Thin Film Solar Panels

There are four basic kinds of thin film solar panels, with each offering its own benefits and drawbacks. And when compared to their more common polycrystalline and monocrystalline counterparts (with average efficiencies between 13- to 16-percent or 15- to 23-percent, respectively) they don't perform quite as well.
Copper indium gallium selenide panels boast an efficiency of 12-14%, putting them pretty much neck-and-neck with CdTe and very close to polycrystalline panels, energy-wise. They're composed of layers of each element (copper, indium, etc) stacked on top of each other — like a cake — and can be spread over a variety of materials like glass, plastic, and some metals.

GW Johnson · 2024-08-24 12:46:15

My inverters tie through a manual switch and a manual circuit breaker directly to the meter installations (I have two, one for the house, one for the shop and my renter). There is no "automatic switch" of any kind! My solar is directly tied to the meter, on my side of the meter. It senses the sine wave coming in from the grid, to synchronize its phase to the grid's phase. If the grid is down, it cannot sense anything, so it makes no AC from the solar DC.

GW

kbd512 · 2024-08-24 14:29:51

I'm going to explain this without any math or million dollar words so that everyone who reads this can (hopefully) understand how / why home solar helps them out with their power bills.

Let's first define some broad general categories of home photovoltaic solar power setups.
1. Grid Tie - Your home solar setup can and does share power with your local electric utility operators
2. Stand-Alone / Off-Grid - Your home solar setup is the sole source of power for your home

Two major kinds of solar power production and storage schemes
1. Solar Only - No power output when the Sun don't shine
2. Solar Plus Batteries - Battery-based electricity storage for use when the Sun don't shine

Two major kinds of photovoltaic solar panel setups
All photovoltaic panels convert photon energy from the Sun or an artificial light source into electrical energy, and they produce DC (Direct Current) power, via the photoelectric effect exhibited by specialized semiconductors. All photovoltaics are special applications of microchip technology designed to produce electrical power. Your home's electrical system, however, uses AC (Alternating Current) power. To go from DC power to AC power, you need a power inverter. There are two primary ways this is done in virtually all real world home solar setups. There are a few users of solar power who opt to use DC power for cost and complexity reasons, but those users are few and far between, and DC power is mostly used by standalone / off-grid solar power setups, typically to power something specific like a well water pump or battery bank.

1. Individual on-panel power inverters to regulate each panel's voltage / amperage / frequency

Pro: Produces more total power throughout the year because the power output doesn't get dragged down to the weakest output panel in the array. There are some limitations to this, as we'll discuss. Imagine that one panel is partially shaded while the others are in full sunlight- this is a common real world issue and the reason why on-panel inverters nearly always out-perform centralized inverters over time.

Con: Having 1 power inverter per 1 panel is more complex, more costly, requires more wiring, the inverter power electronics can and do fail because they're bolted to the back of a very hot solar panel on a very hot roof. Older models were prone to leaking but newer ones are totally sealed from the factory and can only be opened up at the factory. The inverter can shut off the output power at inopportune times, such as during the bright but cloudy days following Hurricane Beryl here in Houston. Due to how these independent little inverters operate, the net effect can be to periodically shut down the array's output entirely if there is either too much or too little output. This is done to protect the connected electronics in your home, but primarily to protect battery power storage subsystems connected to the array. It's also a failsafe not subject to a single point of failure, in the event of an electrical short circuit. Each box contains non-replaceable internal fuses, so if a lightning strike fried a single panel in the array, then the rest of the array continues to function normally.

2. Central inverter with multiple strings of solar panels attached to a smaller number of power inverters than solar panels

Pro: Simpler and cheaper, typically will produce at least some power so long as there's at least some sunlight. These inverters typically last longer than the on-panel inverters and are on-site repairable. Their fuses can be replaced if they blow. Fuses are normally present throughout these home solar systems, between each component of the setup (fuses at the inverter, fuses before any battery storage bank, fuses between the junction box connecting the solar system to your home and the rest of the grid, etc). This is a very good thing, because it prevents electrical fires, but more components always add to the cost and complexity. A centralized inverter is less expensive and simpler to maintain than dozens of smaller inverters for that reason.

Con: Loses some total power production potential when compared to on-panel inverters because power output is limited by the output of the weakest panel's output connected to the inverter for a given string of solar panels wired in series. You might have 20 panels in 2 strings, 10 panels per string, and each string, rather than each individual panel in the string, has a power inverter. The very thing that makes this setup simpler and easier to repair, also hurts efficiency by a bit. The difference may or may not be meaningful. If you live in a desert where thunderstorms and high winds are rare events, then there's probably not much advantage to on-panel inverters. If you live in a place with highly variable weather, then on-panel inverters start to make more sense.

With a central power inverter, if Panel A is producing 12V at 1 Amp, but Panel B is only producing 10V at 1 Amp, then your total output is 10 Volts * 2 Amp. If you have an inverter for each panel, then the inverter steps-up or steps-down the voltage within its ability to do so, so the total output tends to be greater when this situation occurs, which will primarily relate to cloud cover, mornings and evenings, and any problems some specific panel may experience relative to all the other panels in a string.

People like to argue this stuff and what's theoretically possible to do, but I'm talking about real world vs theoretical world.

Someone who knows how to work with power electronics can usually repair a centralized inverter in-place at your home if something shorts out, usually due to overheating. Since a central inverter is also not subjected to the heat of a roof/panel-mounted electronics box, assuming build quality is equal, the central inverter will fail less often. There is no practical way to repair on-panel inverters, so they must be sent back to the factory that made them.

The correct analogy is "adding storage space to an iPhone". There is no such thing. The iPhone's memory chip is literally "built into" the integrated electronics of the phone. You can only replace it. Repair is not possible. A central inverter is more like a traditional desktop computer tower. If something goes wrong, you unscrew the cover, remove the board or component that failed or needs to be upgraded, and then you're back in business.

Grid-Tie Power Distribution
In most home solar setups, there's a junction box (electrical or power electronics switches) which allows power produced by the home solar system to be fed back into the grid when it's demanded. The solar company signs a deal with the local electric utility provider(s) so the homeowner's electricity rates are reduced and permission is granted to feed power into the grid after certification of the equipment, usually to near-zero (you still pay the monthly fees), because the total or net electrical power demanded by the home, over a year (not any specific point in time), falls to zero or near-zero. This means the electric power utility operator doesn't need to ensure as much power is available for your home, which is an advantage to them, because it reduces their marginal operating expenses. It does not mean that the power company gets to shut down power production entirely, it just means there's no wild swing between peak power demand and lowest power demand.

The How and Why Home Solar Makes Sense
Power consumption at a daily level, as well as a seasonal level, looks similar to the Sine wave commonly associated with AC / Alternating Current power. There's a simple reason for this. When the Sun is highest in the sky, it's producing the most heat here on Earth, so AC systems are consuming the most power to keep the house cool. This is very favorable for solar power. When the absolute most power is demanded, then unless it's raining or very cloudy outside, solar panels are also producing the most power output. If the power company could get all the peaks chopped off the demand Sine wave which represents the load on their grid, they could operate in a very simplistic, stable, and predictable manner. Electric generators powered by gas turbines can be run at a more-or-less steady state, which produces the least wear and tear on the machine, and all the electric equipment connected doesn't have surges of power coursing through it, so there is less flexing and repeated heating and cooling of the metal components contained therein, thus fewer cracks of the conductor wiring or other components and fewer equipment failures. Any machine which burns fuel also runs at maximum efficiency when deliberately designed for steady state operation. This is especially true of all turbine-based systems. Gas turbine fuel efficiency drops like a rock when they're not run at maximum output. This is why a jet engine idling can consume almost as much fuel as a much higher power level. If power demand fluctuates between 250MW and 1,000MW, the equipment tasked with supplying that power will wear out and need to be replaced a lot faster than if it was required to supply a constant 500MW.

How can a home solar system actually reduce power demand if it's not meeting demand at any given time?
If your home uses 1,800kWh over the course of the entire year (more power will be demanded during certain months to run AC or heating- seasonal power demand), then the solar array is sized such that it will nominally supply 1,800kWh over the course of a year, or as close as the solar company can get using available roof surface area and angles incident to the Sun. An electrical engineer who knows your power consumption over the past 2 years, knows the site (how much sunlight), knows the angles (where to place the panels on the roof to maximize output over the day) and shading (from both trees and angles on the roof blocking the panels), can design a solar system to come remarkably close to meeting your total power demand over the course of a year. This does not mean your home solar system will supply 100% of your power demand at any given point in time, just that over the course of a full year, the system is designed to produce almost exactly as much total power as you used during the years your electrical engineer has total demand figures for (more historical consumption data is better, and more recent data is weighted more heavily by anyone who understands stats and forecasting), plus a little extra (so that as the system degrades over time, it still covers your total annual power demand over the 25 years the system is anticipated to operate over).

If you're not actually using all of your power from your home solar system at any given time, that doesn't mean someone else in your neighborhood can't use it. In the 100% grid power case, the gas turbines at the centralized power plant has to burn more fuel to produce more force to spin the electric generator. If everyone has home solar and someone in the community is demanding power while someone else is not, then the power "running through the wires" can be shared amongst the homes. The gas turbine doesn't need to produce more output as long as the demand is being met.

There are some limitations to this, and obviously my panels produce nothing at night, but during daylight hours where the most power is demanded, if everyone had roof top solar, then the power company has a predictable fuel bill and operating scheme for their equipment, the gas turbines can be appropriately sized to run at maximum efficiency, and together we make the grid last as long as it reasonably can. I know for a fact that I'm going to continue to use electrical power in my home right now, a year from now, and even 25 years from now. Nothing is fundamentally changing in that regard. We have a cooperative arrangement between the solar installation company, the electric power utility provider, and the power consumers to contain cost and grid expansion requirements.

At an individual site or home level, it's actually pretty easy to supply a given total amount of power per year that most people use, and to account for the relevant factors affecting solar power production, especially when you have your historical power consumption data to use as a guide or measuring stick. That said, each install is a bespoke solution, customized to you and no one else, even though it ends up helping everyone else. It's well nigh unto impossible to ensure that electrical power demand or "load" on the grid is satisfied 100% of the time with a home solar "supply", regardless of demand, at any given moment in time. To that end, batteries are used as power buffers and/or significant onsite storage for surplus power from the solar system, but often times this vital buffer is not included, to reduce total cost to the home owner by increasing power production vs sinking money into storage. As we attempt to scale-up the solution to a national level, this scheme rapidly falls apart, because we're either running a gas turbine 24/7/365, or we have no power. What works well at the home level doesn't work at all at the state or national level, and vice versa.

Absent significant amounts of battery storage, it's impossible to run a state or national electric grid on solar power alone, regardless of how much land or roof space you have to work with. No power output at night makes that statement of fact rather self-evident. This is why photovoltaics-based solar systems will never replace heat engines. They complement the heat engines, albeit a very useful complement when used cooperatively with the utilities providers to keep your power bills lower and more consistent than if you operated off of grid-supplied gas-fired turbines alone.

I view our own home solar setup as a fixed fee for electricity, and a much lower fee than what the power company was charging us, regardless of the provider we opted to go with. We pay a flat $367/month for our home solar setup, plus the fee for the privilege of intermittently drawing power from the grid when we don't make enough ourselves. Our monthly power bills fluctuated between $800 and $1,800 without home solar. I promised no icky math and numbers here, but $367 is less than $1,200. I think or at least hope that most people understand that. I love what my power company provides, at least when Centerpoint decides that they want our money, but I don't think it's worth a mortgage payment all on its own, especially not when we lose power so frequently. Our system includes 67 panels and 2 Tesla Power Walls. It certainly was not cheap, but good things usually cost real money.

Calliban · 2024-08-24 15:15:07

Thankyou GW Johnson and Kbd512 for providing an insight into home solar power. The more I hear about these systems, the more finicky they sound. Where I live in the UK, solar PV power is almost pointless. High cloud cover and a latitude not far beneath the arctic circle, reduces effective capacity factor to about 10%. The sky is almost perpetually cloud covered, with sunshine effectively limited to the three months of summer. A grid tie-in would appear to defeat the point of using solar power, which is to avoid the need for a distributed grid in the first place.

Kris DeDecker of low tech magazine has written an article on the direct use of solar power, without grid tie-in or batteries.
https://solar.lowtechmagazine.com/2023/ … batteries/

He makes the point that inverters and batteries account for 90% of the lifetime cost of a typical offgrid system. But an offgrid system without storage or inverters, would appear to require the use of low voltage DC electricity. What's more, it would have to be consumed as it is generated, with loads added and removed as power generation rises and falls. Some people have experimented with living like this. But it would appear to me to be a substantial departure from the way most people are accustomed to living.

Last edited by Calliban (2024-08-24 15:26:16)

SpaceNut · 2024-08-24 15:25:06

As kbd512 has indicated there is a difference for DC from the panel and a module that converts it at the panel to an AAAC signal to be used at the next device. It is nonsynchronous so it does not go directly to the grid but through other devices. When using AC that is not synchronous from one to another panel other means even direct AC use by the home's devices are also not possible without converting to create a single source AC voltage even if not going to the grid.

Most electricity demand for those working versus the stay at home means it's in early morning and at night once returning from work for the day while solar has produced its peak energy capture.

kbd512 · 2024-08-24 18:52:53

Calliban,

If you live in the land of the blazing hot Sun, as we do here in Texas, then home solar power makes a lot more sense than if you lived in England or Germany. Solar power doesn't make sense (work acceptably well most of the time) everywhere, nor does wind power. Wind turbines would be functionally useless where I live, unless they were mounted atop a pole of colossal height, where the atmospheric wind speeds were much higher than they are near the ground. Kansas, on the other hand, has plenty of wind speed. It also has periodic fast-moving swirling winds which don't do any human-built structure any good.

I wouldn't say that a grid-tie defeats the point of roof-top solar, but I would tell people who think solar power alone can supply all of your power needs at all times to stop deluding themselves about how much power is available and when. As always, solar produces no power at all at night. The cost of a battery storage system capable of reliably supplying enough power to run our home, regardless of time of day or season of the year, would likely cost as much as our home.

There is no economic way for electro-chemical batteries to store enough power, cheaply enough, to make onsite energy storage an affordable proposition for most home owners. The average US home energy consumption per year in Texas for a 2,000ft^2 home is 1,176,000Wh per month, or 14,112,000Wh per year. If all you had was 1 lousy day of energy in your battery bank, it would need to store 38,663Wh of energy. Furthermore, your home solar system would need to supply that much energy every day, regardless of the season of the year.

2,000ft^2 is near 186m^2. Here in Texas, solar insolation averages between 2kWh and 7.2kWh per square meter per day. Solar panels generally convert one quarter of that into electric power, so 500Wh/m^2 to 1,800Wh/m^2 per day. At 500Wh/m^2, you need 77.326^2 to produce your 38,663Wh per day, in order to make it to the next day without running out. Well, what's the problem, you got at least 186m^2 to play with? The problem is that the Sun moves across the sky during the day and some of those panels won't receive much power at some point during daylight hours. This means you'd need to cover most of the entire roof with panels. That implies 93 panels at 2m^2 per panel.

We have a 6,500ft^2 house, but there's really only room for 67 panels. If we didn't care at all about practicality or the panels producing nothing during large portions of the day (costing money to install and maintain, but not saving any), we could absolutely cover our roof with more panels. Our system, with 67 panels and 2 Tesla Power Walls, was around $100K. We'd need at least 3 Tesla Power Walls and another 26 panels, meaning the cost would increase by another 1/3rd, for a home 1/3rd the size of ours and 1/3rd our power consumption. Our previous 2,500ft^2 home cost about $200,000. Would it have made any kind of economic sense to install a home solar system that was more than half of the total cost of the house? Umm... Not in my world, but I'll qualify that by saying I also live in Realitysville, and in Realitysville we don't pay $133K extra for a $200K house. Yes, I'm "weird" like that. Apparently, so are most other sane and rational people.

A lot of people foolishly believe that the cost of the system is limited to the cost of the equipment. The real cost is the installation, maintenance, insurance, and interest / equipment depreciation cost on the loan. Like most people, I don't have an extra $100K rolling around in the seat cushions of my couch, so I pay as I go, the same way most people do. If I find a good deal for my family and purposes, then I take it. If not, then I don't sign my name to the loan. Furthermore, you are operating your own miniature power plant on the roof of your house, so "going cheap" is a better than average way to lose your entire investment, plus your home, and potentially your lives. I won't allow amateurs to work on my home power plant, because the potential cost and liability to me is too high for that to ever make sense.

That begs the question, though, how does a family living in an averaged-sized house cram all those panels and PowerWalls into their property footprint without safety or practicality issues cropping up (like being able to step somewhere on the actual roof to install the panels)?

It's pretty clear that they cannot, because it simply doesn't make economic or practical sense to do so.

Even though our home solar system achieves 100% offset on the power we draw from the grid during the course of an entire year, it doesn't actually "do that" at any specific moment in time. Those 67 panels produce gobs of power over the entire year, yet they cannot run our home AC systems at any specific moment in time. Think about that before you start believing running entirely off-grid is practical, because for most of us it's not. If you had an entire farm plot to work with, then yes, you absolutely could generate all of your own power, provided that you had lots of extra capital to work with.

Ground installation costs on a farm plot might be lower or they might be higher due to the need for panel stands, concrete, and ground clearing, but it's not a DIY job unless you have the knowledge, experience, and professional credentials to get your paperwork in order. If you mess up, the consequences range from expensive to fatal, sort of like learning to fly without professional instruction. They did at least a day of actual testing with the power company in our case. We had electricians from both the solar company and power company working on it. Rule #1 is always don't blow it up or set it on fire. There's a reason professional roofing companies won't touch your roof until the panels come down. Their guys spend all day every day on roofs, but they're smart enough to know what they don't know.

Most people living on farms are superior managers of debt and navigators of byzantine regulations and tax codes, not superior business investors, based upon their returns. Even if you are as shrewd with your money as the average farmer has to be in order to survive and not go bankrupt, in modern times almost none of us live on farm plots. That tends to place practical limits on the functionality of a rooftop home solar system. It's a business proposition, so treat it as such, and only invest your money if it makes economic sense for you, where you live. Treat it the same as you would any other major investment decision, because that's what it is.

SpaceNut · 2024-08-25 14:07:14

Bad news for LFP Battery Health Degrades At Full Charge, Study Finds but I thoink that its true for all rechargeables.

What to know about Monocrystalline Vs. Polycrystalline Solar Panels: What There Is To Know

Calliban · 2024-08-26 15:26:03

Kbd512, An electricity consumption of 14.112MWh per year, is a huge amount of power for a single dwelling. Am I right in assuming that the bulk of this is for air conditioning? My UK house uses between 4 and 5MWh per year, about a third as much. And that is with two of my kids glued to their PC gaming systems for most of the time they are awake. We have a fridge, freezer, several computers, 3 TVs, dvd player, electric oven, etc. I woukd say our power consumption is above average for the UK. What is it that you people do that uses so much juice?

Last edited by Calliban (2024-08-26 15:27:09)

tahanson43206 · 2024-08-27 09:13:41

For Calliban re #19

You've asked a most interesting question, so I enlisted Google to try to find at least some of the answer.

The usage reported by kbd512 looks about right for Houston, Texas, in an average home there.

Google found a web site where data is assembled for the US population, and the value kbd512 quoted is at the high end of average.

That means there are many many homes that exceed that usage.

The usage you reported may show up in the US figures in comparable locations.

Here is a snippet that covers the number kbd512 quoted...;

https://www.eia.gov/tools/faqs/faq.php?id=97&t=3

Frequently Asked Questions (FAQs)
How much electricity does an American home use?
In 2022, the average annual amount of electricity sold to (purchased by) a U.S. residential electric-utility customer was 10,791 kilowatthours (kWh), an average of about 899 kWh per month. Louisiana had the highest annual electricity purchases per residential customer at 14,774 kWh and Hawaii had the lowest at 6,178 kWh per residential customer
Electricity purchases may not represent the total electricity consumption for some residential electricity customers. A growing number of U.S. households have solar photovoltaic (PV) systems on their property and most of the systems are grid-connected net metered PV systems. Net-metered PV systems effectively reduce electricity purchases. In states where there are many residential net-metered PV systems, the amount of household electricity consumption may be a lot higher than household electricity purchases.
The Residential Energy Consumption Survey (RECS) accounts for household-level electricity end use, which includes electricity sales and consumption from on-site PV systems. The 2020 RECS, for example, estimates that in 2020, annual electricity consumption per household in Hawaii—where there are a relatively high number of residential net-metered PV systems—was 7,976 kWh and in Louisiana—where there are relatively few residential PV systems—it was 14,779 kWh. According to the Electric Sales, Revenue, and Average Price report (with data for 2020), total annual electricity purchases per residential electricity customer were 6,446 kWh in Hawaii and 14,407 kWh in Louisiana.
Learn more:
Electric Sales, Revenue, and Average Price (see Table 5.a)
Residential Energy Consumption Survey (RECS) 2020 (detailed data on U.S. residential energy consumption in 2020)
Residential Energy Consumption Survey (RECS) 2020 State data (state-level data on U.S. residential energy consumption in 2020)
Electricity Explained: Use of Electricity
Electricity Explained: Electricity use in homes
Last updated: January 8, 2024, to correct a typo for U.S. average monthly consumption.

What I find surprising is that Hawaii is quoted as having the lowest average rate. I would have expected many other states (like Alaska) to have lower rates than Hawaii. Apparently there is more going on in Hawaii than I realized.

(th)

Last edited by tahanson43206 (2024-08-27 09:50:43)

kbd512 · 2024-08-27 21:57:48

Calliban,

Our house has a pool and 3 AC units. Both the AC units and the pool pump really love the taste of those electrons. We turn most things off in our house when not in use, because they all generate heat.

Calliban · 2024-08-28 04:13:52

kbd512 wrote:

Calliban,
Our house has a pool and 3 AC units. Both the AC units and the pool pump really love the taste of those electrons. We turn most things off in our house when not in use, because they all generate heat.

Given your location, a 10kWp system should generate as many kWh in 1 year as your house uses in 1 year, but not necessarily when you want to use them. What seems to be very expensive is a system that can meet abitrary loads on demand. Looking at panel costs from vendors, the actual panels themselves would cost about $5K. Which to be honest, is cheap as chips. It is all the other costs such as installation, inverters and batteries that seem to be dominate total system cost. It would be helpful to have a complete cost break down for an offgrid system.

My suspicion is that only way an offgrid RE system like this is going to work, is if demand can somehow adjust to supply. That is to say, air conditioning can be designed to store ice and generate ice when the power to do so is available. The way a demand management system would need to work is by dividing loads into three categories: (1) Discretionary loads, things you need to be available all the time (lighting, core refrigeration, television). (2) Dispatchable loads - things that are manually controlled, but can typically wait until power is available (clothes washing, dish washing, games computers, etc); (3) Floating loads - things that the controller switches on automatically when there is excess power in the system. Things like air conditioning, the freezer, fridge, pool pump, water heater, oven. These loads can be designed to store enough energy thermally to allow only intermittent activation. If we can build systems like this and people can adjust their lifestyle accordingly, then a home based RE system could be affordable to most people. But if we have a situation where load is not flexible, then the cost of energy storage becomes unaffordable.

I cannot see any way around this. The only energy storage that is capable of storing energy at scale, affordably and compactly, is thermal based. And the only scenarios where it is useful as part of the system, are those where power demand can adjust to supply. That means avoiding switching certain things on when the power isn't there. I suspect that this will be quite difficult to impliment. But I don't see how RE can be affordable any other way.

Last edited by Calliban (2024-08-28 04:26:20)

SpaceNut · 2024-09-15 09:34:30

Thinking about when the storms take out the grid and the solar could produce power but is not due to missing AC sync field one could open the line and connect a sine wave invertor to that and while disconnected from the grid the home would be powered. Once can use a car battery and connected solar panels to the battery to charge it. without knowing the size of the AC field sync line, one might think that a 100-w unit would be capable of making the needed sinewave for the grid connected unit for home use while the sun is out. Since your design has no battery backup to it.

tahanson43206 · 2024-09-15 09:50:31

For SpaceNut.... re #23

That is an interesting idea and one I hope you will continue to develop.

A factor that seems likely to be a concern is how your system will substitute for load. The McGregor system appears (as nearly as I can tell) to depend upon a load sharing function between the grid and the home. When the panels produce more power than the home is using, the excess is fed into the grid. The system automatically draws from the grid when the home is consuming more power than the panels supply (such as at night).

Your sine wave device might be able to interface with the solar system, but if your device cannot absorb power when there is excess not consumed by the home, the solar system would have to shut down to avoid damage.

It seems to me your ideas are worth developing further. Perhaps there is a way to dump unneeded power to a water tank or other energy sink, but whatever you design must be able to match the excess power output from the system.

(th)

SpaceNut · 2024-09-15 14:35:00

Thats why storage batteries that are part of the power wall that KBD512 matter as excess since when you you want energy that is saved for later.
The frequency of 60 hz is looked at we are in the audio range and that makes the grid unit that GW has a part of an amplifier where the amplitude controls whether you are pushing energy into the grid.

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