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"Gas Armageddon": Energy/electricity prices in EU/UK (and how to deal with them)

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tautech:

--- Quote from: SiliconWizard on August 26, 2022, 06:30:34 pm ---So, not to derail this discussion excessively, but isn't this Great Reset finally rearing its ugly head?  ::)

--- End quote ---
Not without some strong messages from citizens to Gubbermints to pull their heads outta their arse and start running the country like adults.

Gyro:

--- Quote from: SiliconWizard on August 26, 2022, 06:30:34 pm ---So, not to derail this discussion excessively, but isn't this Great Reset finally rearing its ugly head?  ::)

--- End quote ---

The problem is that it needs to a global reset, partial resets lead to various 'components' being in unknown states - the s/w can get very confused!

tom66:
Is a home battery and solar system worthwhile now?

So I took the solar data from my location which I got from Solcast API (https://solcast.com/).  I then fit this against a reasonably pessimistic model of a 4kWp solar system on an ideal roof orientation. The system is modelled to generate 3,970kWh per year which is about average.

The Python script takes the insolation data, calculates solar generated in half-hourly intervals, and models battery charge and discharge.  If there's a shortfall in the first iteration (it appears that there is insufficient solar for that day) it adds additional charging during an off peak period (currently set to 2:30 am to 6:30 am, though it could vary.)  This is a little inefficient as it should aim to top the battery up in full by the end of the off peak, probably by varying charge current.

This is a very simplistic algorithm, I haven't attempted to add in any kind of iterative solution solver to improve upon the "first iteration".  I'm reasonably sure that if you know, or can estimate, the sun and cloud cover for tomorrow, and have a model of daily load and know the starting state, that it's possible to perfectly calculate charging times needed.  For now, I make a very simplistic optimisation: if the projected solar energy for that day is insufficient, I charge a number of 30 minute slots in that off peak period.  The reality is that there are a few days where the energy from the day before is actually enough that this charging is not necessary.  But it is better to over-estimate expenditure than to under-estimate it.

The results are very interesting (to me, at least!) because they justify such a system rather easily.

Assumptions:
- Sun is similar to 2021-2022 season in any given year
- Panel efficiency 20%, panel area 20m^2
- On peak cost of 60p/kWh, off peak cost of 15p/kWh (assuming the 'Octopus Go' sweetheart rate does not remain forever at 7.5p/kWh)
- Off peak charging time available is 4 hours (charge rate ~3kW)
- Daily usage of 12kWh electricity excluding EV (charged in off peak period) and no heat pump
- Daily usage is assuming timed high loads can be shifted into off peak (e.g. dishwasher, tumble dryer) - in other words, it is the "unshiftable" demand
- Battery size 9.5kWh (GivEnergy LiFePO4) with charge efficiency 91%
- Battery does not require heater in winter (mount in insulated garage >5C year round)
- The 5kW output of the battery is enough to cover ~98% of usage and therefore I don't need to account for forced grid use here

Pre-system cost is £2,591
Post-system cost is £273

Yes, it saves nearly £2,300 per year for an ordinary user - or about the same as the price cap will rise by this year for both electricity and gas.  If the system costs £10k, then it pays back within 4.5 years.

In addition to the 'savings', it contributes 911kWh of energy into the EV battery in the case when there is too much sun that day to go into the home battery. (This assumes that all of this can be used.  Probably it could also be diverted into the hot water tank or something else if needed.)  That's around 3,000 miles of 'emissions and cost free' driving.

If I change the parameters somewhat:
- Off peak 30p/kWh, on peak 90p/kWh

Pre-system cost is £3,917
Post-system cost is £535
Saving £3,382

Reflecting a short term high price but still a low off peak price.

A payback time of under 3 years.

However, if the off peak price rises considerably, say:
- Off peak 60p/kWh, on peak 90p/kWh

Pre-system cost is £4,040
Post-system cost is £1,036
Saving £3,004

Surprised me that the benefits are still there.  It's really all down to the solar.  The off-peak is nice, but the solar is *great*.

Now let's assume things return to 'normal':
- Off peak 6p/kWh, on peak 17p/kWh

Pre-system cost is £699
Post-system cost is £106
Saving £593

As can be seen, the savings vanish if the on peak price is low.  The payback time is going over 15 years in this case, well beyond the warranty of the battery.  Perhaps it would make more sense if there was a heat pump, with high daily consumption, though extra batteries would likely be required. The pre-cost does not include any benefit in the summer from EV charging which may change the maths a little bit, but probably not substantially.

I have attached the script in Python if anyone is interested in playing around with it.  The solar data can be fetched from Solcast, you will need to sign up for a trial account and input your address to get solar data.

Now to convince the other half to spend £10k on this kit ... that may be the biggest challenge!

Attached outputs are for the 60p/15p scenario.

tautech:

--- Quote from: tom66 on August 26, 2022, 11:12:22 pm ---Is a home battery and solar system worthwhile now?

--- End quote ---
In the current climate certainly as it provides some insulation against all the energy supply uncertainty.
Your call as to the value you might put on that.

Edit to add
We have a solar powered data relay 'high site' installation with just three 300W panels in series for maintaining SLA's in a 24V series/parallel 4 battery installation of some 320Ahr capacity and my in just 2 1/2 years logging shows 1.5 MW of solar energy poked into the batteries......that's a lot of energy for free other than the initial investment.....ROI is entirely another matter as no other energy source was available at this remote location ~1km from the grid.

Marco:
If electricity prices become high enough for long enough to earn back a battery in short order, I'm afraid society in its current form will collapse. So rather than a battery you should invest in emigration. I'm going down with the ship though.

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