Some advice needed Additional Solar vs. Additional Battery vs. Wind turbine

viewofthehill · 06-09-2022 3:36pm #1

Hi All,

Sorry I didn't know where this would fit best so I've created a new thread. Apologies if it should go elsewhere and feel free to move it if needs be.

First the background

I've been following the threads on here for a while now and recently had Solar PV installed (August 8th). Thanks to the help and advice of some of the folks on here (@MAULBROOK and @yankinlk in particular I finished up with a 8.36kWh system with a 5kWh battery installed for just north of 12K (after grant). The installation is split 4.56 kWh SSE and 3.8 kWh WSW so we get good coverage across most of the day at the moment. Due to August being a particularly good month I passed 1 MWh of production about an hour over 4 weeks after install.

Over the past two years we have had an annual usage of 12 MWh with two of us working from home. We have a heat pump and everything in the house heating, water, cooking etc. runs off electricity. We recently moved back to the office and as a result our usage has appeared to have gone down so over the course of the year I would expect the 12 MWh to reduce also. For this period (Aug-Sep) in this year and previous years we have used:

Year Day Night Days

2020 743 272 60

2021 763 473 58

2022 370 195 36

I have been looking at the data coming back from the system to see a potential payback date. I know that the last month isn't fully representative of how it will work over the next 12month - 10 years but the data has thrown up a number of interesting things already. We have moved the hot water boost from early in the morning circa 7:00 to between 11:00. This will be moved back in winter when production dips to avail of the night rate. From the charts below there is also something happening late on a Friday evening which I am trying to track down. Maybe someone has some pointers as to what it may be.

As with everyone else who has installed solar I am now beginning to look at tinkering with it. To that end I have a question related to my next potential move. I have seen the threads debating the merits or otherwise of batteries, the payback periods, FIT etc. My question is related to whether a wind turbine would complement the existing system or if you would be better investing in another battery/more solar panels. Has anyone done some calculations around this?

Additional battery

While the DIY route would be much cheaper I wouldn't be comfortable with setting one up. I currently have a 5kWh battery which discharges to 20% so 4kWh usable. The graphs above show that this has proved very useful in savings due to the discharge over the course of the day and in the evenings. A second battery may take me through the night at the moment but maybe redundant for the months of May/June/July. It would also only add an additional 4kWh which would need to be charges during the winter to use during the day.

Additional solar panels

For the cost of an additional battery I could possibly put in an additional 8 solar panels giving me additional generation of 3kWh-3.2kWh. I am currently over producing and have sent almost 600kWh to the grid. These panels will produce extra during the winter months and will reduce the day rate kWh that need to be imported.

Wind Turbine

I know that wind turbines are dependent on how much wind is in the area. We are in an area with no obstructions behind the house (the direction that the wind primarily comes from) and the wind is funnelled between two hills so at a height of 5m it can be fairly breezy. If a wind turbin was to generate 100w consistently for 24 hours a day it would be the equivalent of filling a 5kWh battery with night rate. The one that I was looking at was the Tesup Atlas (it comes in at roughly the same cost as a Battery) although I have seen the thread earlier this year about them so may be on the lookout for something similar if anyone has any ideas.

I suppose the question is if you had a budget of 2500 - 3000 for your next solar/renewable investment would it be daft to put in a wind turbine? If I am going off completely in the wrong direction feel free to let me know. As I said the advice I got from here has got me to where I am so I really appreciate and value it.

Apologies for the long and rambling post.

DC999 · 06-09-2022 6:14pm

Hey, there's a lot in this. To boil it down what's the biggest thing? Is it to work out what gives the most bang for your buck to do a 'phase2'? So to add more battery, more solar or add wind for 1st time?

If you've only got solar live a month (as do I), you and I are still very much learning. There may be a 4th option - do nothing for now (as in don't spend more money) and learn your setup and consumption (IE, spend your time). As most on this forum have extended over time, I'm also keen to see what they suggest for newbies like us :)

Said setup now is 8.36kWh system with a 5kWh battery. I've only 5kWP which is all our house can fit. So 8 is a decent size already.

So other missions could be around spending time, not money:

Could you increase self consumption so you export less and don't need to buy it back at a dearer rate later in the day? And get ready for load shifting as we head into the autumn
Start to setup automation (to turn stuff on and off to use power at cheap night rate or when battery at X% charge)
Use less power. 12 MWh you said you use a year. That's twice what our house and EV together use - but we've no heatpump and cook on gas (for now). That's going to save you in Day1

viewofthehill · 06-09-2022 9:32pm

Thanks for the reply @DC999. Not really looking at spending money at the moment but more to see what options are available and what advice people with solar for longer would give. The current install is oversized for the summer but was more to help out when the days are short and the solar radiation isn't the best.

We moved into the house in at the start of July 2020 (a new build) and before getting solar installed I had been watching the electricity bills since then. We had load shifted what we could to night rate e.g. washing machine, dishwasher, dryer and have since moved them back to operating during the day the washing machine and dryer that we got are smart devices and so we can run them remotely (provided there is clothes in them) and the dishwasher can be run using a delayed timer now that we are back in the office. We currently have a base load of 350w which equates to just over 3MWh a year which can't be moved.

I have considered looking at automation but I am just wondering if there are only incremental gains to be got from it and whether they are worth it. e.g. if I spend 10hrs per year looking at automation, at minimum wage that equates to €105 or ~ using an additional 440kWh at current EI day rates (23.5c), moving 850kWh from day rate to night rate (11.5c) or 1100kWh if production was fed into the grid (FIT of 14c) and had to be imported at day rate.

I have had a look back at the spreadsheet i am using to monitor the electricity usage and our usage peaked at 12.8MWh in the twelve months leading up to December 2021. 12MWh was the average 12 monthly usage across the period that I had been monitoring. Looking at the current usage on the meter for 12 months Oct 21 - Sept 22 (Bill is at the end of the month) we are currently at 10.1MWh with 25 days left. Adding the consumed solar generated during August and estimating 20kWh for the remaining days would bring us in at 11MWh so use is going down. I would expect that some of the additional was due to drying out the house (first time heat pump was run in anger would have been December 20 - February 21)and working from home.

To answer your initial question: what's the biggest thing? It's if I was to consider something at a later stage to improve what is already in place what would that be?

We have space to add panels on the roof, add ground mounted panels, increase the battery size or add a small wind turbine. Are there merits to all of these or are there any obvious no's to any of them e.g. excessive noise from turbine? redundancy of battery for large parts of the year? limited time generation of PV (requires sun and daylight)? wind speed requirement for turbine to produce anything usable? additional inverters needed for additional solar strings or turbine etc.

Ubbquittious · 06-09-2022 10:26pm

The Tesup company has a plethora of terrible reviews: https://www.trustpilot.com/review/tesup.co.uk

I mentioned the icewind turbine before though it's not quite on the market yet. It has a fighting chance of paying for itself at some stage: https://icewind.is/residential/

Until now anyway domestic wind turbines were only really for off grid use as on grid they'd never pay for themselves. Though if electricity prices keep increasing and the turbines improve only marginally then that could all change.