Even in the depths of British winter my solar panels'll still happily convert what little sunlight we get into delicious, free-range, organic electrons. Nice!
Most of our domestic energy use is in the evening. So, when I'm out at work I can schedule the tumble dryer, robot vacuum cleaner, and WiFi rice-cooker to consume energy when the sun is shining. The rest is sold back into the grid for my neighbours to use.
Wouldn't it be great to capture that energy and use it to power my lights and games console in the evening? Yes! Enter the Maslow - a 2kWh wall mounted battery designed to capture solar power and put it to use when it is most needed.
The Maslow gobbles up the surplus power and stores it for later use.
I received a subsidised Maslow battery as part of Project ERIC.
Project ERIC (Energy Resources for Integrated Communities) is an initiative bringing solar PV power and smart energy storage to up to 100 homes in Rose Hill, East Oxford. Project ERIC is led by Moixa Technology and Bioregional and is part-funded by Innovate UK.
It's a relatively svelte box - smaller than a normal domestic boiler - and fits neatly onto my interior wall.
Here it is before installation and without any batteries.
As you can see, the batteries are designed to be replaceable. If they die unexpectedly, or technology leaps ahead, you should be able to keep your existing installation and just swap out the cells for something newer.
A couple of screws - and a bit of swearing - and it was fitted.
Installation took around 3 hours. The battery needs its own RCD in your consumer unit. A few holes had to be drilled in order to get all the wiring hidden away.
The fans on the side run when the batteries are charging or discharging. They're a little louder than a typical PC - and will be easily drowned out by a boiling kettle or rumbling tumble-dryer. You probably wouldn't want this installed in a bedroom or living room - but it's fine for a kitchen or loft.
They're needed for cooling these chunky capacitors.
Down in the bottom of the unit, you'll find the fairly unremarkable control circuitry.
Wait... wait a moment! Is that...? OMG! This thing is RASPBERRY PI POWERED!
Wooo! I think this is the 5th Pi I have controlling something in my home ?
There's a WiFi antenna which runs to the outside of the unit. You can also connect directly to the Pi's Ethernet port if you don't have a strong WiFi signal.
Hidden behind a panel is a full range of blinkenlights.
A mini-USB port is present for debugging purposes, along with some diagnostic LEDs. Apparently there's also Zigbee for controlling smart appliances in the future.
Network and API
As part of the Project ERIC trial, I've agreed to have my battery's energy usage monitored.
The Maslow collects details of usage every minute, these data are then combined to provide an overview of what our village is consuming and producing:
I also get access to a personalised dashboard - which will hopefully show more details soon!
There's nothing really to control on the battery - it just sits there doing its job. There is an API, more details in a future blog post!
Because I'm on a trial of this hardware, the total cost of the Maslow battery and installation was £600 (including VAT@ 20%).
What do you get for that?
A typical mobile phone battery holds around 0.015kWh. My electric car has a battery capacity of 19kWh. My house's idle usage overnight (lights, chargers, servers, devices on standby) is around 100 Watts. So a typical night (2200 - 0600) will use around 1kWh.
My electricity costs me 13.08p / kWh - sign up to Ovo Energy and we both get a £25 Amazon voucher.
So, assuming the battery is fully charged once during the day and then fully discharged overnight, how long before the device pays for itself?
£600 / (£0.1308 * 2) ~= 2,300 days.
2,300 / 365 = 6 years 4 months.
At the unsubsidised price of £2,000 the repayment period is around 21 years. That's essentially the guaranteed lifetime of most solar-power systems. It also assumes that energy prices stay static.
Of course, the solar panels don't always generate enough - let alone enough surplus - to fill the battery:
— Edent's Solar Panels (@Edent_Solar) February 13, 2016
There's no doubt the Maslow is an expensive "lifestyle" product. It's for saving the planet rather than fattening the wallet. Built in to the cost of a typical home it could be a real game-changer in how energy is used in this country.
As an aside, the UK Government pays me for every kWh the solar panels generate. They don't measure the actual amount I export. So the Maslow doesn't reduce the Feed In Tariff (FIT) payments.
OK, other than offsetting my grid usage, what does this big ol' box do?
- Powering DC lighting. I decided not to go for this option. I already have energy efficient bulbs, so the extra cost for replacement didn't make sense for my needs.
- DC Power Circuitry. I've not yet installed this, but it should let me charge USB devices without needing to do a costly AC/DC conversion.
- Works during a power-cut. For safety reasons, the Maslow won't power normal household sockets during a power-cut, but it will allow you to use the aforementioned USB sockets and LED lighting. Handy in an emergency
- WiFi for monitoring usages. Which of course means…
- An API available for HACKING!
There are number of alternatives to this sort of technology.
- Divert to immersion heater. I currently have a Solar iBoost which heats up my water and reduces my gas usage.
- Build it yourself! If you have lots of spare batteries and are a qualified electrician.
- Car storage. At the moment, I've been using my electric car to store surplus electricity - but I'm not always at home during the day. I can't "reverse the polarity" and feed back from the car into the house.
- Tesla Powerwall - the elephant in the room!
Tesla battery has the cachet of the Tesla brand - but hasn't yet been released to the UK public. At around US$3,000 for a 7kWh model, the cost/power ratio is pretty good - but it is significantly larger in size to the Maslow.
The Tesla is only generally available in the USA, so it will be very interesting to see what their price is for the UK market. The Maslow is designed for typical UK use, which may be different from Tesla's focus - UK houses don't tend to have air conditioning, for example.
I've only just had the batteries installed - but it's obvious that the Maslow provides a vital way to reduce peak grid usage from domestic properties. Even if it is a little costly.
I'm delighted to be part of such an innovative trial - I'd love to see every home in the UK generating and storing their own energy.