6 ms·

Mine produces 6-8 kW on summer days, in New York. I still buy most of my power from the utility, but my roof is maxed out.

robomartin 4y ago
Ah, sorry to hear that. I opted not to build the array on the roof. Too complex. Too many issues I did not want to deal with, including damage to roofs reported by neighbors. This is what it looks like from space: https://i.imgur.com/FLvXi0w.png https://i.imgur.com/FLvXi0w.png 40 x 325 W panels feeding two SMA 6000W inverters. That's enough because you'll never make peak label power. The most I've seen is 11 kW peak. Lots of reasons for this. One of them being the permit authorities limiting the tilt angle of the array to 15° due to zoning/planning/whatever code. No big deal. I am adding a third inverter and more panels this year. Not sure how things are done in New York. Here in SoCal it isn't as simple as selling excess energy back. The accounting is like going to the casino, it's heavily tilted in favor of the house. They are paying a useless amount of money per excess kWh. With NEM-3 coming-up, the incentive to install solar are mostly gone (which is a serious problem). I have been looking at shifting into the tiered power metering plan. I can't do it until I take the time to fully model it and understand what will happen. A quick top-level analysis says it should actually be better than NEM TOU plans because you never go into high tiers at all, particularly with a decent system. To make things worse, the true-up calculation is just killing people these days. We have great relationships with a dozen of our immediate neighbors. We talk about stuff like this all the time. I can't think of one who is currently happy with solar. Please understand that none of them bought their system. They were sold a small leased system that was barely adequate. So, they end-up with something like a $150 to $200 per month lease payment, another $150 to $300 per month in energy bills (because they can't make enough with solar) and, on top of that, they get hit with hundreds of dollars every 12 month when the true-up calculation is done. It's crazy and NEM-3 isn't going to help at all. Going back to what you were saying... > There is no need for "ten times" overbuild. Instead, you just need a backup generator you can fuel at need. I hope you are not proposing that every solar owner should have a backup generator. For one, those things are horrible polluters. Please note that the 10x overbuild is based on simple mathematical realities. One of the examples I gave was the need to double the system to store energy for night use and a multiplier of 1.5 (a total of 3.0) as a result of energy being the integral of the ideal-case parabolic generation profile. In other words, these numbers are not a matter of my opinion, this is physics. If you want constant power 24/7 you have to start there. Once you calculate all other factors the number very easily goes above 10x. Another example, here's a basic derating calculation: https://i.imgur.com/KbS0aev.png https://i.imgur.com/KbS0aev.png This math requires increasing the array size by 1.5x again. We go form 3.0 to 4.5. Etc. If you do the math, 10x is an understatement. > Building storage after you have enough renewable overbuild to charge it from I understand what you are saying. However, there's an intersection of curves where things just do not line-up. It's already happening. Utility companies are raising prices and consumers are going to get hurt (NEM-3, again). I forget the exact numbers. When I installed my system 1 kWh was about $0.15 off-peak. Today, depending on the plan, you are in the $0.28 to $0.35 range. As more solar is installed the balance will cause serious side-effects. I don't think we fully understand what will happen. > A low duty-cycle backup generator should be, above other considerations, cheap. Don't you have one? They are cheap. I don't need one. My system allows me to generate power (up to 4 kW) if the grid goes down. That's why I chose the SMA inverters. When I add a third inverter this will increase to 6 kW. Yes, of course, the sun has to be up and no clouds, etc. I will eventually add batteries. I just doesn't make any sense right now. The ROI is horrible. Also, if you do the math, the amount of energy you have to store to literally weather the storm (if you want to be 100% off-grid) is insane. Looking at what happened in December/January, we are talking something in the order of 500 kWh. And, of course, this would require an equally massive array to keep the batteries charged. My conclusion is that going 100% off grid with 24/7/365 reliable power and no compromises is pretty close to a fantasy. Before concluding this is crazy, take a look at this calculation from a battery manufacturer: Their conclusion is you need 56 kWh to survive just FOUR days if your home requires 10 kWh per day. My air conditioning system alone burns approximately 5 kW and, in the heat of summer, it is on some 12 to 16 hours per day. That alone blows-up the 10 kWh/day budget. Still, if we stick with that and decide we need to be 100% reliably off-grid for 30 days, not 4, the number is 420 kWh. In other words, my estimate isn't crazy at all and the idea of homes existing 100% off-grid is a fantasy for most. Which brings me full circle to having to have 100% reliable external power sources that can deliver 100% of the power a town or city might require at any given moment for short or long periods of time. That's the part I can't reconcile. I can play with solar. I can throw money at it. However, at scale, not sure. That's why I talk about nuclear. Pick any other technology. My conclusion is solar alone isn't going to happen. Not at scale.
- moloch-hai 4y ago
  There is nothing wrong with running a backup generator when mains power is down. Solar alone obviously can't happen, most places. Solar + wind + hydro + (sometimes) geo + (even) old nukes + storage + xmission line + backup combined-cycle gas turbines will, instead. Backup gas turbines will burn NG at first, synthetic ammonia or hydrogen later. Getting 100% off-grid is not a goal worth the extra cost, for most. For anyone without access, or with unreliable mains, a backup generator is just prudent. Batteries, if you have any overbuild, mean you spend on mains or run your generator less often. At utility scale, with regional-grid tie-in, calculations come out differently. Maybe the gas turbine runs part of most weeks, this decade, rather than once or twice in winter like your backup generator. Wind and transmission line complement solar. Battery cost is radically less than 2 years ago, and still falling. If you haven't checked lately, prepare for a surprise.
  - robomartin 4y ago
    > Solar alone obviously can't happen, most places. Exactly my point. Yet, beyond that, the analysis shows you have to have 100% backup rated at 100% the required peak power output. That's the conundrum. For every deliverable GW of of solar you have have a GW of backup. And so my question is simple: How does that make any sense at all? Let's make sure we don't engage in a hand-wavy arguments though. Wind: Regional, seasonal and varies throughout the day Hydro: Not available everywhere, highly seasonal. Check out this chart [0]. Hydro is susceptible to water availability. Hoover Dam lost 33% of it's output capacity for this reason --about 600 MW. Geothermal: Sounds great. Only 0.4% of US utility scale generation Old Nukes: 20% of US power generation. We have over 80 of them. Only three of them in the west [1] (which is astounding) Transmission Lines: They are only good for about 300 miles. Power is relatively local. Hoover Dam feeding Los Angeles is about 250 miles straight line. Combined Cycle Gas turbines: About 20% of US capacity. None west of Texas. Anyhow, the point is that it is easy to list all of this power generation options and lose sight that they are not available everywhere and adding capacity is nearly impossible. In fact, if you look at the maps showing distribution of the above power sources in the US it isn't too hard to conclude that the west coast is not in good shape at all. Here's the kicker: I haven't even introduced the reality that 100% conversion to electric powered vehicles will require the US to double it's power generation capacity. This is monumental. Conceptually, it means we have to fully duplicate our existing generation and transmission infrastructure. Frankly, I don't know how we make that happen. Please don't say solar. Once again, nuclear keeps coming back as a source that is impossible to ignore. We need so much power to support electric vehicles that we would need to build 1200 new 1 GW class nuclear power plants. This is impossible. Clearly a hybrid system will be required. Again, no, solar can't do it. It can be a part of it, but it just can't rise up to the occasion. [0] https://en.wikipedia.org/wiki/Hydroelectric_power_in_the_United_States#/media/File:US_Monthly_Hydro_Power_Generation.png https://en.wikipedia.org/wiki/Hydroelectric_power_in_the_Uni... [1] https://en.wikipedia.org/wiki/Nuclear_power_in_the_United_States#/media/File:NRC_plant_locations_Oct_2021.png https://en.wikipedia.org/wiki/Nuclear_power_in_the_United_St...

robomartin 4y ago

Ah, sorry to hear that. I opted not to build the array on the roof. Too complex. Too many issues I did not want to deal with, including damage to roofs reported by neighbors. This is what it looks like from space: https://i.imgur.com/FLvXi0w.png https://i.imgur.com/FLvXi0w.png 40 x 325 W panels feeding two SMA 6000W inverters. That's enough because you'll never make peak label power. The most I've seen is 11 kW peak. Lots of reasons for this. One of them being the permit authorities limiting the tilt angle of the array to 15° due to zoning/planning/whatever code. No big deal. I am adding a third inverter and more panels this year. Not sure how things are done in New York. Here in SoCal it isn't as simple as selling excess energy back. The accounting is like going to the casino, it's heavily tilted in favor of the house. They are paying a useless amount of money per excess kWh. With NEM-3 coming-up, the incentive to install solar are mostly gone (which is a serious problem). I have been looking at shifting into the tiered power metering plan. I can't do it until I take the time to fully model it and understand what will happen. A quick top-level analysis says it should actually be better than NEM TOU plans because you never go into high tiers at all, particularly with a decent system. To make things worse, the true-up calculation is just killing people these days. We have great relationships with a dozen of our immediate neighbors. We talk about stuff like this all the time. I can't think of one who is currently happy with solar. Please understand that none of them bought their system. They were sold a small leased system that was barely adequate. So, they end-up with something like a $150 to $200 per month lease payment, another $150 to $300 per month in energy bills (because they can't make enough with solar) and, on top of that, they get hit with hundreds of dollars every 12 month when the true-up calculation is done. It's crazy and NEM-3 isn't going to help at all. Going back to what you were saying... > There is no need for "ten times" overbuild. Instead, you just need a backup generator you can fuel at need. I hope you are not proposing that every solar owner should have a backup generator. For one, those things are horrible polluters. Please note that the 10x overbuild is based on simple mathematical realities. One of the examples I gave was the need to double the system to store energy for night use and a multiplier of 1.5 (a total of 3.0) as a result of energy being the integral of the ideal-case parabolic generation profile. In other words, these numbers are not a matter of my opinion, this is physics. If you want constant power 24/7 you have to start there. Once you calculate all other factors the number very easily goes above 10x. Another example, here's a basic derating calculation: https://i.imgur.com/KbS0aev.png https://i.imgur.com/KbS0aev.png This math requires increasing the array size by 1.5x again. We go form 3.0 to 4.5. Etc. If you do the math, 10x is an understatement. > Building storage after you have enough renewable overbuild to charge it from I understand what you are saying. However, there's an intersection of curves where things just do not line-up. It's already happening. Utility companies are raising prices and consumers are going to get hurt (NEM-3, again). I forget the exact numbers. When I installed my system 1 kWh was about $0.15 off-peak. Today, depending on the plan, you are in the $0.28 to $0.35 range. As more solar is installed the balance will cause serious side-effects. I don't think we fully understand what will happen. > A low duty-cycle backup generator should be, above other considerations, cheap. Don't you have one? They are cheap. I don't need one. My system allows me to generate power (up to 4 kW) if the grid goes down. That's why I chose the SMA inverters. When I add a third inverter this will increase to 6 kW. Yes, of course, the sun has to be up and no clouds, etc. I will eventually add batteries. I just doesn't make any sense right now. The ROI is horrible. Also, if you do the math, the amount of energy you have to store to literally weather the storm (if you want to be 100% off-grid) is insane. Looking at what happened in December/January, we are talking something in the order of 500 kWh. And, of course, this would require an equally massive array to keep the batteries charged. My conclusion is that going 100% off grid with 24/7/365 reliable power and no compromises is pretty close to a fantasy. Before concluding this is crazy, take a look at this calculation from a battery manufacturer: Their conclusion is you need 56 kWh to survive just FOUR days if your home requires 10 kWh per day. My air conditioning system alone burns approximately 5 kW and, in the heat of summer, it is on some 12 to 16 hours per day. That alone blows-up the 10 kWh/day budget. Still, if we stick with that and decide we need to be 100% reliably off-grid for 30 days, not 4, the number is 420 kWh. In other words, my estimate isn't crazy at all and the idea of homes existing 100% off-grid is a fantasy for most. Which brings me full circle to having to have 100% reliable external power sources that can deliver 100% of the power a town or city might require at any given moment for short or long periods of time. That's the part I can't reconcile. I can play with solar. I can throw money at it. However, at scale, not sure. That's why I talk about nuclear. Pick any other technology. My conclusion is solar alone isn't going to happen. Not at scale.

moloch-hai 4y ago
There is nothing wrong with running a backup generator when mains power is down. Solar alone obviously can't happen, most places. Solar + wind + hydro + (sometimes) geo + (even) old nukes + storage + xmission line + backup combined-cycle gas turbines will, instead. Backup gas turbines will burn NG at first, synthetic ammonia or hydrogen later. Getting 100% off-grid is not a goal worth the extra cost, for most. For anyone without access, or with unreliable mains, a backup generator is just prudent. Batteries, if you have any overbuild, mean you spend on mains or run your generator less often. At utility scale, with regional-grid tie-in, calculations come out differently. Maybe the gas turbine runs part of most weeks, this decade, rather than once or twice in winter like your backup generator. Wind and transmission line complement solar. Battery cost is radically less than 2 years ago, and still falling. If you haven't checked lately, prepare for a surprise.
- robomartin 4y ago
  > Solar alone obviously can't happen, most places. Exactly my point. Yet, beyond that, the analysis shows you have to have 100% backup rated at 100% the required peak power output. That's the conundrum. For every deliverable GW of of solar you have have a GW of backup. And so my question is simple: How does that make any sense at all? Let's make sure we don't engage in a hand-wavy arguments though. Wind: Regional, seasonal and varies throughout the day Hydro: Not available everywhere, highly seasonal. Check out this chart [0]. Hydro is susceptible to water availability. Hoover Dam lost 33% of it's output capacity for this reason --about 600 MW. Geothermal: Sounds great. Only 0.4% of US utility scale generation Old Nukes: 20% of US power generation. We have over 80 of them. Only three of them in the west [1] (which is astounding) Transmission Lines: They are only good for about 300 miles. Power is relatively local. Hoover Dam feeding Los Angeles is about 250 miles straight line. Combined Cycle Gas turbines: About 20% of US capacity. None west of Texas. Anyhow, the point is that it is easy to list all of this power generation options and lose sight that they are not available everywhere and adding capacity is nearly impossible. In fact, if you look at the maps showing distribution of the above power sources in the US it isn't too hard to conclude that the west coast is not in good shape at all. Here's the kicker: I haven't even introduced the reality that 100% conversion to electric powered vehicles will require the US to double it's power generation capacity. This is monumental. Conceptually, it means we have to fully duplicate our existing generation and transmission infrastructure. Frankly, I don't know how we make that happen. Please don't say solar. Once again, nuclear keeps coming back as a source that is impossible to ignore. We need so much power to support electric vehicles that we would need to build 1200 new 1 GW class nuclear power plants. This is impossible. Clearly a hybrid system will be required. Again, no, solar can't do it. It can be a part of it, but it just can't rise up to the occasion. [0] https://en.wikipedia.org/wiki/Hydroelectric_power_in_the_United_States#/media/File:US_Monthly_Hydro_Power_Generation.png https://en.wikipedia.org/wiki/Hydroelectric_power_in_the_Uni... [1] https://en.wikipedia.org/wiki/Nuclear_power_in_the_United_States#/media/File:NRC_plant_locations_Oct_2021.png https://en.wikipedia.org/wiki/Nuclear_power_in_the_United_St...