Hornbeam Hedge Planting

For the ‘farm’ hedges around the boundary of the site, I’m happiest with Hawthorn – which is what the boundary hedges were originally and still mostly are now, just with a few (big) gaps. Some of the Hawthorn has given way to Blackthorn, which isn’t quite as good but provides an interesting contrast. (The main problem with Blackthorn is that it spreads by suckering and the whole hedge tends to grow wider over the years. It also responds less well to hedge-laying than Hawthorn.)

For other hedges within the site, especially near the buildings, I generally prefer Hornbeam. While it’s a UK native and happy to tolerate wet ground (much better than Beech which looks very similar) it can be kept trimmed into a tidy, formal shape.

The only sensible way to plant a hedge more than a few metres long is using bare-root plants but those really need to go into the ground while they’re still dormant – which ideally means before the end of March (and even then the plants will need to have been kept in cold storage). The existing Hornbeam hedge to the South of the House lost the leaves it had kept over winter and started to bud around mid-March, indicating that new bare-root hedging would likely also be coming out of dormancy at a similar time.

Ever since the Outbuildings got completed, with the ground around them looking rather flat and bare, the plan has been to plant a hedge along the back of the parking area to the North of the Garages, to act as a wind-break and to help separate that area from the planting beds further North. That was waiting on the fence along the Eastern boundary being installed, which happened at the start of March.

What should have been a fairly quick job of preparing the ground turned into a much bigger task when it became clear the ground had been heavily compacted by all the building plant traffic. When it gets compacted, the ground here turns into a solid layer which is almost waterproof – resulting in a thin layer of mud on top of an impermeable layer below. That’s no good for planting into so the compacted layer needed breaking up (generally with a pickaxe) and forking over. To make matters worse, under the compacted layer there was a lot of demolition rubble from the old barn buildings (which had been there since the House was built) – many barrow loads of full-sized bricks and half-sized concrete blocks – so that had to come out to check the ground wasn’t compacted below it. In some places that meant digging down nearly a full metre, to expose the original topsoil.

With the made-up ground consisting mostly of subsoil, rather than topsoil, it needed plenty of organic matter adding – of which there is a plentiful supply from several years of composting the hay cut every August from the wildflower meadow. The main problem with that is judging how far all of the disturbed ground and compost will settle, so that the hedge ends up level with the adjacent parking area. Ideally I’d leave it to settle for a month or so but then that would really be too late to be planting bare-root hedging.

Previously I’ve bought bare-rooted Hawthorn and Hornbeam from a local supplier but they were out of stock of Hornbeam for this season so I used mail-order supplier Best 4 Hedging based in Chorley, Lancashire, who were also a bit cheaper. I’d hoped that by placing an order on a Monday I’d avoid the risk of the plants being stuck in-transit over a (potentially warm) weekend but they ended up shipping on the Friday and I wasn’t expecting them until the Monday but I was pleasantly surprised by DPD delivering on the Saturday.

The plants were just starting to sprout leaves – which helped to confirm none of them were dead. They were very similar to what I’d planted before, with the expected variation in heights and stem thicknesses; quite possibly they had come from the same nursery as before. I kept them in buckets of water in the dark for a couple of days while finishing the preparation work and then planted them over a couple more days. The hedge is 24m long and I’d planned on 5 plants per metre (40cm spacing in two staggered rows 40cm apart) for 120 in total. It always feels like vandalism to cut off the top 1/3 of each one after planting, but this is important:

  • To encourage more shoots to sprout from the base, for leaf cover closer to the ground
  • To reduce the number of leaves needing water from the root system while that recovers from the shock of being transplanted
  • To reduce the effect of wind loading while the plants get settled – especially since I don’t bother staking them

It’s quite hard to get a good photo of a line of brown sticks against a brown background; I’ll take further photos once they get some decent leaf-cover.

120 bare-root Hornbeam plants forming a hedge by the Garages, with a mulch layer to help retain moisture

With the rainwater harvesting system feeding two outside taps by the garages it proved easy to water in the new plants using a hose and spray nozzle. While the cost of 1,000 litres of metered mains water is only about £2.50 it’s good not to have to give any thought to the water usage. I was also careful to thoroughly soak the compost mulch covering several times, in the hope that by being wet that would be less likely to blow away in the 40mph winds forecast for a few days after planting.

Tesla Powerwall Energy Export Option Setting

The Tesla Powerwall 3 integrated inverter-and-battery system is meant to be ‘smart’ in learning about solar generation and energy usage patterns, but it’s not proven to be as clever as I was expecting – notably in terms of Exporting from the Batteries to the Grid. One downside with the Powerwall is that its control algorithm is very much a ‘black box’ so it’s difficult to check if it’s working correctly – or even what “correctly” is expected to look like.

During the Winter, with modest solar PV generation and heat pumps running in both the House and the Outbuildings – plus all the other usual electrical loads – the Powerwall was effective in fully charging the batteries by Importing from the grid overnight, taking advantage of 6 hours of the Intelligent Octopus Go off-peak import rate of £0.07 per kWh and then using its battery to service all the electrical demand throughout the remaining 18 hours, generally avoiding all peak-rate Imports. Any solar PV generation – which could be significant on a sunny-but-cold Winter day – was Exported to the grid (in real-time).

At the end of March, with the heating off and much more solar PV generation, that model is no longer appropriate. In particular, with the distribution network operator imposing an Export limit of 5.5kW but the potential to generate more than 16kW at Noon, there’s a requirement to temporarily store much of the PV generation in the battery and then export that in the evening – to create the headroom in the battery to accept further solar generation ‘tomorrow’. If that doesn’t happen, the solar PV generation has to be curtailed once the battery gets full.

My expectation was that the Powerwall would have visibility of a solar PV generation forecast for ‘tomorrow’ and choose to Export to the Grid from the Batteries in the evening, since it knew all the generation would never be consumed on-site. But that’s not been happening: the Powerwall never exported any of the energy stored in its battery.

Within the Tesla iOS App, I see options to set the Operational Mode, choosing between:

  • Self-Powered, which “reduces the reliance on the Grid”
  • Time-Based Control, which “uses stored energy to maximise savings”

I’ve also been seeing two Advanced Options:

  • Permission to Export, which can either be Yes or No
  • Grid Charging, also Yes or No

With both Permission to Export and Grid Charging set to Yes, in Time-Based Control mode I saw all the Solar PV Generation being Exported to the Grid (up to the Grid Export Limit of 5.5kW, with additional generation above that limit being used to charge the batteries). However, none of the energy stored in the battery (either from local solar PV generation or from an off-peak import from the grid) was ever exported.

Tesla’s documentation for the Advanced Settings in the Mobile App includes the following text:

Energy Exports

Some energy suppliers allow Powerwall to send energy back to the grid and claim credits during peak times. If ‘Energy Exports’ is not available in the Tesla app, your energy supplier does not allow Powerwall to export energy to the grid for any Time of Use purposes.

How It Works

If your Powerwall is allowed to send energy to the grid, the following energy export options will be available in the Tesla app:

Energy Exports OptionDescription
Solar1Powerwall will only export solar production to the grid during high-cost time periods.
EverythingPowerwall will export both solar production and stored Powerwall energy to the grid during high-cost time periods.

When set to ‘Solar,’ your Powerwall will only use stored Powerwall energy to match your home load consumption when the price of energy is expensive. Use this setting if you want to earn credits while also keeping energy stored in your Powerwall to reduce reliance on the grid.

When set to ‘Everything,’ Powerwall will send both solar and Powerwall energy to the grid and will continue to discharge to your set Backup Reserve. Use this option if you want to maximise savings.

1 Default setting

However, I’ve not been seeing anything that looks like that Energy Exports option in the iOS App and – based on the behaviour I have been observing – the PowerWall has been acting as if that setting was on its factory default of ‘Solar’.

While investigating third-party control options to implement the behaviour I ideally wanted, I installed the Home Assistant integration for the Tesla Fleet API. (I’d tried installing that previously, when the Powerwall was first commissioned, but was thwarted by an obscure error. I finally got around to investigating why it failed and applying a work-around.) Unlike the Tesla iOS App, this integration exposes the Energy Exports options. I actually only spotted that because the setting initially defaulted to ‘Never’ and I was puzzled as to why the normal daytime export behaviour wasn’t working on the day after installing the integration. The names of the Energy Exports options in the Home Assistant dashboard for the the Tesla Fleet integration are slightly different from in the Tesla documentation:

  • Never – which presumably equates to “Permission to Export” being set to No
  • Solar only – which presumably equates to “Solar”
  • Battery – which presumably equates to “Everything”

Initially I was hopeful that changing this setting via Home Assistant would influence the behaviour of the Powerwall, but that wasn’t the case. However, with the benefit of more experience of how the system has been operating and the clarity of the highlighted text in the Tesla documentation, I was fairly certain my unit had been commissioned with the wrong setting.

I contacted my installer, who contacted Tesla (who seem to be the only people able to correct configuration errors made during commissioning) and they changed the setting that was prohibiting export from the batteries. Now I’m seeing a third option under Advanced Settings in the Tesla iOS App, which is giving it permission to export from the batteries.

It looks like that setting was changed about 24 hours ago. As a result:

  • The Powerwall barely charged from the grid during last night’s off-peak tariff period – even in Time-Based Control mode – meaning the battery had spare capacity to accept much of the excess solar generation during the daytime
  • The Powerwall was aggressively exporting all through the early evening, maintaining the maximum permitted 5.5kW of Export even after the solar generation dropped to zero
    • It’s only just now (at 20:00) started reducing the export to maintain enough charge to get it to the next off-peak import time slot (at 23:30) with the configured 20% ‘buffer’ of minimum charge to maintain, in case of a grid outage

So the behaviour has definitely changed – for the better. I’m expecting it to take a few days to re-learn the ideal behaviour and tweak its optimisations.