Category: solar

I’m going to try to get into the habit of more frequent updates to my ongoing solar-farm-project, because stuff is starting to happen now. Here is a brief run-down on whats happened since the last blog post on April 3 2023.

Well we had a meeting about the farm progress on 12th May, and there was a lot to discuss. We finally had the details from the DNO about the earthing requirements for the farm, so our high-voltage engineer could look at that and then design the earthing layout for us.

There was then some bad news about the inverters. We were going to use Solis inverters, but the ones we wanted were no longer available, so the plan was now to switch to Huawei inverters instead. These are Chinese, and some people have views of using kit made my Huawei but I don’t. I really don’t think there is a backdoor in them that will let the Chinese communist party turn off my solar farm, but I do think there are a lot of conspiracy-theorists that probably do :D. This change to different inverters might seem like no big deal, but its actually hellishly complicated…

Changing inverters means you suddenly have a different number of strings, and the way the panels are wired up is suddenly different. You might assume (as I did) that the panels were in nice neat rows, and there was an inverter for each row, or each two rows. No! Apparently thats not how its done, especially on undulating land. Its actually a lot more complex than that, and the positioning of the inverters and which panels get attached to each inverter is hellishly complicated, and done by some complex solar-farm management software.

Anyway, this was generally a good news meeting. Mounting frames were ordered, people booked in to do work.

There was then a LOT of emails back and forth about voltages and another meeting on 26th May. This is where stuff got super involved…

I had assumed that you always connected a solar farm at high voltage, and needed a transformer up to 11kv, at which point the DNO takes over. BUT NO. Suddenly the DNO says they have changed their internal regulations regarding what size inverters they let connect directly to them, and it had gone from 50kw to 200kw. Our inverters are about 110kw, so they were suddenly chill about us effectively giving them nine cables from 9 110kw inverters at low voltage (about 410v I think).

This is a BIG DEAL, because it vastly changes who pays for what, and whats included. Suddenly we arent doing ANY high voltage cabling, or switchgear, and we wont need a transformer at all. This saves a LOT of money in terms of connection offers. Apparently I will get a new connection offer tommorow, and the old one will be cancelled.

In theory this is good, but I wouldnt be surprised to find that the lower connection offer is offset by all the other materials and labor price increases that have happened since we started. Sure, its GOOD news to have a number actually come DOWN instead of up, but I’m not getting too excited by it.

Its hard to convey just how complex a project like this is. The change to the offer would mean that we can move our (much smaller) substation closer to the one for the DNO. That means the site layout can be slightly smaller, which means less fencing (which would be cheaper!). However, it also totally screws up our earthing design, because we now have different stuff, in a different place, at a different voltage… arggghhh. The one bright spot is that apparently moving our substation will not be a planning issue. Thank Christ.

Anyway, the truly exciting news is that a ground survey was done 2 days ago, and the ‘setting out’ engineer will visit the site this week, I think wednesday. Thats the very last step before people show up to build an access road and start building stuff with concrete bases and installing ground mount frames and the security fence. This is all getting very close!

The current plan is for setting out on 31st, then the fencing, then access road. 26th June is pencilled in for the day they start building the ground mount frames. I will nip up there when that happens and take a look at it all, and take a stupid number of photos. Its looking quit likely that we get energised this year, and start generating power, and maybe (gasp) earning revenue this year!

So, it turns out there has not been a proper solar farm update since this one, back when we finally got the planning permission. It probably feels like nothing has happened since, which is more accurate than you might think, but stuff is changing much faster now, so time for an update!

For anyone new to the blog, I own a small company that is building a 1.2MWp solar farm in England as a side-project to making video games. 1.2MWp is tiny by solar farm standards, but it will power 300 homes, so its not *that* tiny. This is the first time I’ve ever got involved in any sort of ‘infrastructure’ project, so I’m learning as I go along…

I knew back in October when we got permission, that nothing was going to happen straight away, because any construction site that is in that part of England, in winter, in the rain and the mud and the rain and also in the rain… is basically untenable. I can not remember the exact number of large truckloads of equipment we need to get to this field, but I know its more like 30 than 20. Put that together with all the manpower that has to get there, and its just going to be an absolute mudslide of horrific proportions. When I first visited the site, the landowner met me on a quadbike, and I can see why…

(Imagine this…but with a thousand billion times more rain and mud)

Anyway, there was a lot of other stuff that needed doing before we actually stick things in the ground, so there has actually been some non-visible progress. Most of the progress was, sadly, in things I didn’t even know we needed.

The contractor who will build (and likely operate/maintain) the solar farm basically builds an array of low voltage (about 400v) solar panels, all of the inverters and the cabling to a substation. Thats basically all they do. They know how to wire up a LOT (3,024) of solar panels at a voltage of about 400v. Thats considered low voltage. The actual UK power grid at this size, tends to be operating at 11,000v (11kv) or 33kv or even higher. That means you need a transformer that steps up the voltage to 11kv, and switchgear that handles all that stuff. You then need to cable it from your substation to the DNO substation, which is where their responsibility begins.

It feels weird to me that this means 2 substations, but apparently it does. It also means that you need a high-voltage expert to design and handle all of the 11kv stuff, which goes beyond ‘ouch that hurts’ and right up to the ‘all that was left was the flaming boots’ level of danger, so I guess its no surprise you need a 3rd party expert for that stuff. Also I discovered that big transformers are full of oil. Who knew?

So…stuff has now got more complicated because the new structure of this project is now:

• Positech Energy (my company)
• The site construction contractor
• The landowner (farmer)
• The Distribution Network Operator or DNO (Grid people)
• High Voltage Consultant

No doubt during construction a bunch of other 3rd parties will be subcontracted to the construction contractor, but thats their problem. Also, eventually there will be an insurance company, plus the people who buy our electricity through a PPA (Power purchase agreement). Hilariously, that may happen through a PPA broker, so there may be yet another party involved. Are you starting to see where your electricity bill goes yet? :D

Anyway…so we now have a high voltage consultant who I deal with directly, but who has to liaise with the construction company and also the DNO, and this involves hilariously complicated email chains where everyone is waiting for everyone else until I step in and yell WHY IS NOTHING HAPPENING, but hopefully in a politer tone :D.

So…moving on from the fact that we now have a high voltage consultant, lets talk about all the other sudden expenses and complications. Ladies and gentleman, I introduce you to the excitement of pullout-tests. Apparently, you have to do pullout tests. Who knew? This is basically paying some engineering experts to go bang some metal posts into the field at a variety of points, then do their best to pull them out again, and measure how much force is required to pull them out. They use special machines and gadgets:

You get a rather tedious number of photos like this, and the eventual TL:DR; of it is that ‘its fine’ which is good to know, albeit a very unfulfilling way to spend £6,795. Yes really. You can buy a very nice guitar for that. Why are pullout tests needed? well they determine what kind of ground mount kit you will need to keep the panels in the ground. Why so important? well solar panels are actually pretty light, and catch the wind like crazy, and we have over 3,000 of them. We are basically anchoring a giant expensive sail to the top of a hill in the midlands. If we don’t secure these puppies nicely, we are just one storm away from them all turning up in Liverpool one day.

Anyway, after all the pain and stress of paying for pullout tests, comes the new excitement around earthing studies. Yes earthing studies. Did you not know solar farms need to be earthed! haha, you fool. Yes of course, we all knew that *loud coughing*. Its to stop a big lightning strike pulverizing the whole farm. Did I mention we are sticking 60 tons of solar panels on the top of a remote field? Anyway, in order to work out HOW to earth the farm, you need to know the resistance of the soil, which apparently, is a thing that varies.

A lot.

Anyway, thats of course another expense, and its all very depressing, and it takes time. Not only that, but TWO completely different companies carry out earthing designs for separate parts of the installation. The DNO (grid people) design the earthing for their substation, and our HV contractor designs the earthing for our bit. Its totally separate. This seems nuts to me, and ripe for optimisation, but I’m not an electrical engineer so maybe there are reasons for this.

Anyway, it means you get sent exciting diagrams like this:

I think we all understand this right? *louder coughing*. It also means you get a design for how all the fancy underground earthing stuff will be arranged, which is apparently generally in a grid pattern, presumably because you are earthing a LOT of stuff, and a single earth rod stuck in the ground isn’t going to cut it:

Oh, in other news I actually have the final quote for the install of the farm. I’ll give a proper breakdown once the farm is constructed, but you will enjoy the hilarity of reading about when I got the quote at 6PM on Friday, with a VERY ambiguous sentence in it, that led me to believe the farm was going to cost £450,000 more than I anticipated. I did not sleep at all Friday night, and was *relieved* on Monday when this was clarified.

Oh how we laughed

The final hilarious piece of news is that due to changes we had to make to the plant layout between getting planning permission refused, and then granted, I have 200 more solar panels than I need. I am still being charged monthly to store them, and this is not fun. I THINK I might be able to stick 8 of them in my driveway to replace my old 12 year old ones, but I’m not sure about that yet. The others will likely be sold to the construction company, at cost (still a net loss as I’ve stored them for 6 months+).

Anyway… the short version of this blog post is that there is PROGRESS. We are anticipating making the first 30% payment to the construction company today, which will mean we can plan actual install dates, and actually order the ground mount kit, inverters and other stuff like cabling. We will use 15km of DC solar cable, for example. Thats a lot of cable.

The good news is that stuff looks like its starting to actually happen now. I have been told that the cutout-switch has already arrived to the town next to the farm, and some other equipment used by the grid connection company has been ordered already. This is a very *good sign* as it means the grid connection will happen this decade, at least.

TL:DR; Gamedev is easy. Building stuff is hard.

I’m lucky enough to be the proud owner of a 9.5kwh battery in my cellar. Its a GivEnergy battery (A UK company, although the actual battery is predictably made in China). Its AC-coupled, which means it sits on the ‘house’ side of the fusebox/consumer unit. We got it installed about 5 months ago and its been super awesome. Not flawless by any means, but its just so cool as a gadget for someone like me.

There are many reasons to get a home battery. Its a cool gadget, its also an incredibly strong way to reduce your energy bills (we basically run our whole house 24/7 on off-peak electricity at 75% off), and its also a great thing to partner-up with solar panels to ensure you use all that free power and don’t go exporting it to the evil energy company for a pitiful rate. I have to admit, although I was fully aware that we exported a lot of power on those days we were out, or we were not running much stuff, I had totally underestimated the impact. I’m currently running a big desktop PC/Monitor, router, wifi boosters and a bunch of other stuff, all from solar, on a cloudy day in march in the UK, AND filling the battery slightly…

Obviously the real reason to get a home battery is because you get to obsess over charts and stats:

I’m going to talk a bit more about the economics of the battery though, rather than the coolness of it, or its usefulness in balancing the grid and helping enable more renewable energy.

The economic bonus of my battery is it lets us buy off-peak electricity that costs (currently) £0.12 per kwh as opposed to peak power which costs £0.43 per kwh. In other words, each unit of power we use saves us £0.35. We use roughly 600kwh per month, but I reckon half of that is for the car, and can be done off-peak through charger scheduling regardless of the battery. So that leaves 300kwh a month or a saving of £105 a month, or £1,260 per year at current electricity rates.

There is an additional economic benefit though, which is that we are self-consuming all of our export. To look at how we manage this, I just need to look at the total solar->battery flow for the last month, which is about 40kwh. Thats energy that would previously have been wasted (exported to the grid, but not metered, so the amount doesnt matter). Thats another 40 * 0.43 so £17.20 a month, or a total of £206 a year.

So the income from our battery, at current prices, is 206 + 1260 = £1,466 a year. The installed cost for the battery was £6,720. So the payback period is 4.5 years. Thats really not bad, given the battery will definitely outlast that. This is also with a pretty rubbish old array of terrible 12 year old solar panels. So it seems like the economics of home battery storage are pretty good.

However…

Now lets take a look at grid-level storage, and the size that I was considering. For those new to my blog, I run an energy company that is building a 1.2mwp solar farm here in the UK. Originally we were considering battery storage, but dropped the idea. We were originally looking to add a 500kwh, later increased to 583kwh battery, in a shipping-container enclosure that was AC-coupled to the farm. We are export-limited to 900kw despite peaking at 1.2kw, so this would be a good way to do peak shaving. I blogged about how that works in detail here.

So why are we not doing it? Basically its the economics. They just do not work, for that scale, at the current time, for a variety of reasons. The main one is that the costs have gone up, but also the cost of larger storage systems have gone down. It looks like economies of scale are massively at work here.

From what I understand, a 583kwh battery unit like the one pictured above is basically deployed as a kit. You get a lot of equipment, including pallets full of batteries, and a shipping container enclosure for all the gear, and then its assembled on site to create a finished, grid-connected 583kwh battery. The installation of this is about £28k out of a total installed cost of roughly £370k.

Lets pick apart the finances of this!

Firstly, a 583kwh battery is the same as 9.7 Tesla model 3 standard range batteries. A brand new Tesla model 3 standard range in the UK costs £43,000. 9.7 of those cars costs £417,000. That is MORE than the grid battery…but Jesus Christ its not MUCH more, and the 9.7 cars come with stuff like wheels, doors, touchscreens and…other car stuff. There is NO WAY that the cost to Tesla for making/buying the batteries in a model 3 are anything close to as high as people are being charged for a grid connected battery.

Whats going on?

Actually, the economics seem to be the case that grid-connected utility storage is being manufactured in a grossly inefficient way, and hugely overcharged for, especially by companies not called Tesla. Lets take a look at the real core of the problem by looking at a battery in a Tesla:

The actual batteries are the little cylindrical cells. They are being slowly changed to be a different configuration, but the same design principles apply: pack the batteries in with as efficient a volume-utilization as possible. Note that its actually much more safety critical in a car to prevent battery fires than in a shipping container sat in a soggy field, so if anything, this is the ultra-conservative and inefficient Tesla battery pack. Also…its a car, so weight REALLY matters (whereas with stationary storage we absolutely don’t care about weight), so thats another constraint. What we are looking at here then, SHOULD be the really inefficient way to do things.

But how are things done for grid scale utility batteries? Well… let me show you :D. This is a lithium ion battery for grid storage:

Thats an 8.1kwh battery. Not enough? It doesn’t matter because we can put them in groups in a rack!

Thats still not enough though, so we can then put the racks in a box!

And so it goes on, with what seems to be a Russian-doll approach to stacking boxes inside boxes inside boxes, until the amount of casings, handles, surrounds, spacers, racks, shelves and other non-battery components becomes ridiculous. Worse still, it seems that a lot of these are still being *assembled on site*. This is, as I am sure you must be aware, ludicrously inefficient.

This is the Tesla Megapack:

Its still racks-in-a-box, for now, but its not built on-site, or in a ‘room’ where you can walk down an aisle. its a big solid block of batteries (plus supporting equipment) that is manufactured like this at their factory. The whole thing is shipped as a single already-connected block, that you then hook up to your grid connections. No pallets, no wasted space. No lengthy install.

This is just a lot of tech-geek inside baseball until you realize the economics of it. The best way to find out the *real* price for these things is to look at recent installs. There was a recent one in the UK: https://driveteslacanada.ca/news/europes-largest-battery-energy-storage-project-opens-in-uk-using-tesla-megapacks/ with 196 megapacks for £75million. That comes out at a per-MWh of installed battery cost of £222k. Thats 42% cheaper than the quote I got for a 583kwh pack.

So the answer is simple right? Just ditch the battery provider you got a quote from and use Tesla? No. The megapack STARTS at 3MW. Thats a £666k installed cost, on top of the solar farm. It *might* make sense if the output of the grid connection was higher, and the farm itself was larger, but nobody would couple a 3MWH battery with a 900kw limited 1.2kwp farm. It would just be idle too much of the time to justify the expense.

We are still in the early days of grid-connected storage. Its accelerating like absolute crazy right now, so we are getting there…but there is a lot of change happening. As an investor in green-tech, I cannot see any other grid storage company surviving after the next 2 years other than Tesla. (The megapack is not surprisingly sold out for the next 2 years). The grid-storage business is VERY price sensitive. You cannot just shrug your shoulders with a 42% cost difference…

So how does that leave me? Well it leaves me building a solar farm with, for now, no battery storage (although with planning permission to add it later if the numbers change). I would love to revisit it when BESS prices drop, and definitely will. I think we are going to see a real push to make those systems cheaper, and thats just based on design optimization and economies of scale, not even considering better battery chemistry or any tech breakthroughs.

For home storage though, its a laughably good deal. If you can afford a home battery, get one.

I’m currently in the throes of building a 1.2MW solar farm somewhere in England. Its an adventure, to put it mildly :D. So far the planning process and bureaucracy has taken just under 2 years. In that time a lot has changed.

Originally the plan was for a 1.2mwp solar farm, and a battery of either 256kwh or 512kwh. The current situation is that I’m evaluating a 583kwh battery (they can basically pack a bunch more cells in there now), but the economics have got a bit trickier and it may not actually be viable. This does not mean the project itself is not viable, the farm likely still is profitable (I hope!).

First things first, I’ll explain why any of this would make any sense. You cannot just rent a field, fill it with solar panels (assuming the farmer lets you, and planning permission is granted), and make a pile of money. Its not that simple. (And trust me: none of that is simple). The main problem you face is the grid connection. Basically solar farms go in fields, so we are already limited to relatively rural locations. This means that the land is large enough, and also its not going to upset too many people. Our site is surrounded by fields and hills and generally…nothing, so there were zero objections. This is all good news..

…but it also means you are on the edges of the power grid. If you are REALLY lucky, you find a site that has a field to rent, thats rural, but also just-so-happens to be a site where a major grid connection cable runs right through it. This is super ideal, and no, there no sites left like this any more in the UK because all the canny early developers have already snapped them up :(

So…we end up with a perfect field, planning permission, and a happy landowner, but we are basically connected to the rest of the grid by what amounts to a thin USB cable (not really). This is the point at which you ask the grid to upgrade that line and send you the bill, they do, then you laugh at how they accidentally added a few zeroes to the bill, and then you start to cry. Basically upgrading a power line is a nightmare. They cant just add heavier cable and be done. That cable may then sag too much in summer, or be too heavy, so you need new pylons, and then the ground under the pylons is too weak so you need foundations and omg expenseahontas.

In practice, that means that the local DNO (power company) has told us ‘you can generate 900kw at any moment from here but no more’, and thats AFTER we pay for a major grid upgrade. This sounds nuts, but when you think about it, if a power cable was only ever built to supply 2 farm houses, its not ever expecting a power flow of more than about 40kw total maximum. Then suddenly we arrive on the scene with 3,000 solar panels and want to push 20x as much power through those cables…

What does this have to do with batteries?

You might have noticed the difference between our 1,200kw solar farm and the 900kw limit on export. Well spotted. Its quite glaring isn’t it? Actually, this is exactly what most people do, and if you have solar panels at home, you do it too. Its called inverter under sizing.

The inverter is the box that converts DC to AC, and is the device that determines the maximum power that can come from your solar panels. In many cases, its rated BELOW the maximum output of your panels. This must seem insane…because surely that means at peak sunshine some of your power is just wasted right? YES. This is exactly what happens, and its normally because the bigger inverters are very expensive, and the PEAK output of your solar panels only triggers quite rarely, maybe for just 1 or 2 weeks in summer around midday. This means that the extra spend on the ‘bigger’ inverter might not be worth it.

Example: You have a choice of a 2kw inverter or 2.5kw inverter. The difference is $1,000. You have 2.5kwp of solar panels. Which do you choose? Well its actually hellishly complex. You need to model the output of your panels for every hour for every day in a typical year, and then ‘clip off’ the top portion where output would have been above 2kw. You then need to value that power at whatever you get paid to sell it, or what it would have cost you to buy it. You do that for the lifetime of the inverter, then work out if its a good deal.

I’m currently basically doing a similar thing, except the limitation for me is export limits, not inverter sizing. Our site will have 10 inverters anyway, and the bigger you get, the more granular you can be with how many you have. (For those curious, yes, thats like 300 panels per inverter, but each inverter supports a bunch of strings).

What does this have to do with batteries?

Well batteries let you cheat the system! They can do it in home installs, with what they call DC-coupled batteries, and you can do it at the grid/utility scale with batteries the size of shipping containers. (I’m evaluating a 20ft long one). Before I get into this, I need to list the different ways the battery might make sense in our solar farm. The battery would generate revenue basically 3 ways:

Frequency support services:

This is where the national grid basically pays you to act as a sort of ‘cache’ or ‘buffer’ for the grid. If they suddenly have slightly too much power, then dump it on you, then grab it back a bit later (maybe even a few seconds or minutes). They do this to keep the electricity grid at 50hz, to prevent every transformer in the country going bananas and maybe even failing. This is a constant battle, fought every second of every day. Here is a chart of the last 36 hours of it:

You can make money from these services, just by having a battery connected to the grid, and being registered to rent out your battery to act as a local buffer.

Time-based arbitrage stuff

You might think the price of electricity is fixed for your current contract term. Ha. Yes, at the consumer level it is, but behind the scenes, the wholesale price of electricity fluctuates like crazy, not only each month, or each day, but each 15 minutes. And it fluctuates a LOT. You can decide to ‘keep’ some of that solar power you generated at midday and sell it later. In fact in theory this can be hugely profitable, based on the current volatility. Again, here is a price chart the last 36 hours:

In that chart, the price gyrated between negative £70 (They pay YOU to use power) to positive £200 for a MWH. In theory, if you could buffer the whole farms output, and only sell it at the peaks, you would make decent money

Peak-Shaving

This is a system where you take that extra power that you are not allowed to export, you buffer it in the battery, and trickle it out later. This transforms the usual bell curve of solar output into a different shape:

We fill the battery with the ‘red’ energy, then trickle it out later to extend the peak output duration of the site. This energy would otherwise be totally lost, and we would not earn a penny for it!

Ok, so these are three ways storage can make money alongside your solar farm. What the problem? The problem is two-fold. Firstly, there has been a HUGE increase in the amount of grid-connected storage in the UK, which means lots of batteries bidding for the same grid services regarding frequency and price arbitrage. That means that naturally, the profits from these mechanisms have dropped. There are a lot of VERY big companies doing this now, and tons more on the way. Plus, there are other technologies that you compete against. The main one would be hydro (basically a gravity-water battery), but also there are experimental things like gravitricity, and companies working with flywheels and other tech. Its VERY volatile.

Secondly, the price of the battery has gone fucking nuts. In 2 years, the price has gone up 50%. Thats crazy. This may partly be due to the EV revolution, which is scooping up all those lithium ion batteries I was hoping to pack my shipping container with. It might also be related to components shortages for power electronics (lots of chips in a stationary battery), and general inflation for stuff like shipping and labour to install a concrete base and so on…

So right now, with the first two potential battery income streams kinda poor, we have to think whether the basic and most obvious one (peak shaving) is actually worth it. It looks right now that a 583kwh battery cost is about a quarter the total cost of the entire project.

That MIGHT mean its just not worth doing. Sure, being curtailed at peak output for a few weeks each summer may suck, but the big question is how much? I don’t have access to the data yet, and do not have software that accurately measures it, nor is it likely worth the hassle of buying any. I am digging further.

The maths I need is pretty simple, IF you have the modeled data: Given the output each day, for 25 years, what amount of KWH is curtailed on the site given a 900kw power limitation. I then need to guess the market price for this and compare it to the battery install and maintenance cost for 25 years. (I know, its optimistic to expect the electronics to last 25 years, but hey).

Hopefully it DOES make a convincing case, because if not, I basically have to scrap the idea of a battery, or at least wait and see if prices fall. I can still install the solar farm in the meantime.