There’s something a bit magical about generating solar electricity yourself. By the simple act of the sun coming up every day, there is energy arriving on Earth, ready for us to convert to usable, sustainable electric power, ready to top up an electric bike or any other appliance. Richard Peace shares his experience of converting that solar panel power generation into a top-up for his electric bike batteries, even while mobile…
I’ve run through what I think are the three main broad approaches home generators might choose to take to help themselves to some of that lovely green energy that’s available just about every day (if you have a large enough panel setup even on the dullest of winter days you will get some solar energy and on a glorious midsummer day you’ll be overwhelmed with it).
These approaches are:
There is further good news; the solar industry is now big business so that means some pretty cost-effective prices and products that are more efficient than ever – so it’s easier than ever to get a meaningful amount of energy from a home setup.
A final note before we dive into a bit more detail; the solar panels I’m talking about here are photovoltaic (PV) panels that generate electricity when the sun’s rays hit a semiconductor in the panel (usually in the form of silicone cells). Solar thermal panels are not relevant here as they don’t generate electricity; with solar thermal, the sun directly warms a heat-transfer fluid which circulates through tubes in the panels, which then produces hot water for your house. And whilst solar thermal panel costs have remained relatively high, solar PV panel prices have tumbled over recent years.
This is undoubtedly a very simple and efficient way to charge e-bike batteries, but unfortunately there are no e-bike companies I know of that manufacture this system so it’s in the domain of those happy to fit and use kits and to take responsibility for sourcing and assembling components themselves. It involves a single solar panel plugged into a small, lightweight charge controller, which then plugs directly into your electric bike battery.
As kits are usually modular in form and most are made for the end user to fit them themselves I find it a bit surprising that only one company – Grin – are promoting solar products alongside their kit offerings with which they can be charged.
How does it work? You need a solar panel and a compatible charge controller with connectors that plug into both your panel and the battery. That’s it. I must stress this won’t work with the vast majority of systems out there and whilst the very competent kit DIYer could assemble a whole system it’s probably best to at least go with a charge controller and compatible battery as sold by Grin.
I have successfully been using a panel-to-bike-battery solar system for a few years. Currently, it comprises an Ecoflow 220W, 21V rated folding panel, an Elejoy 400W step-up controller and some Grin-sourced 36V batteries used to power a Brompton kit.
It works well in bright sunny weather but if you want to use the system in cloudy but bright weather I would recommend the greater efficiency of a rigid solar panel (these are generally far cheaper than folding or flexible panels too, watt for watt), though that means the system then becomes much less portable. For mobile use the ultimate choice would be a lightweight, efficient but super pricey Powerfilm type panel.
Pros
Light and quick to set up
Efficient – this is a DC to DC system so with a good MPPT charge controller efficiency can be in the 90%s (by contrast all other routes for charging an e-bike via solar mean going from DC panels to AC then back to the DC battery on the bike, giving significantly less efficiency).
If you use a flexible solar panel you can carry the system around with you.
With a fixed base rigid panel it is the cheapest option here
Cons
You need to source and assemble all the parts yourself and to have the requisite knowledge and confidence in your own ability.
In the UK’s climate it’s not really a feasible proposition to cut your house off from the grid and go completely solar. It is however not only possible but practicable and (compared to a larger grid-tied system) affordable to hook up some solar panels on a garage, shed or lawn and easily generate enough power to charge e-bikes and other relatively low power devices for much of the year.
There are two broad options;
1. An ‘all in one’ so-called powerbank or powerstation which entails simply plugging in your solar panel or panels at the back and your e-bike mains charger at the front. Ecoflow are one of a number of firms that make so-called ‘powerbanks’ (amongst much else).
Whilst these sound like no more than battery packs they are much more; they can be readily charged by solar panels with a suitable wattage rating and the biggest capacity ones like the EcoFlow Delta 3 Plus that I tested can power not just e-bike chargers but much more power- hungry domestic devices and even smaller power tools.
The Delta 3 Plus has a rated capacity at just over 1kWh and it’s intuitive and easy to use with the display telling you just what’s going on in terms of solar input and power output and a capacity remaining in % figures in nice big figures. The Plus model I tested was able to take more solar input than other variants at 1,000W so two large rigid panels on a sunny lawn meant superfast recharging.
One word of warning though; don’t expect to get the full rated Wh capacity out of the powerstation – there will be efficiency losses depending on things like ambient temperature (cold reduces battery performance of course) and the efficiency of your e-bike charger. I got around 750Wh from the Ecoflow 1,000W system battery on a summer day depending on what e-bike I was charging – still a very good reserve of power that will give a full charge to an average sized e-bike battery.
This is no fault of the powerstation battery but a natural consequence of changing electricity from DC battery power to AC power to use a mains charger then back to the DC power stored in your e-bike battery. All powerstations work in a similar way. The unit generally performs well in independent reviews.
Pros
Easy to use
At 12.5kg it is reasonably portable
Can be used even when the sun is not shining
Cons
Powerbanks are not modular as DIY systems are; if out of warranty and a component breaks then it cannot simply be swapped out as it can with a DIY system, described below.
Not as efficient as a solar panel direct to battery system (the first method described)
2. An off grid DIY ‘build’ involves sourcing panel, charge controller and batteries yourself along with the requisite size wiring, fuses and switches. Knowledge and expert advice is critical to doing this safely and ensuring the system works as it should, especially if you are stringing solar panels together to produce higher voltages.
Here is not the place to go into the detail of this, rather just to give an overview of a relatively small home system I put together. I sourced parts largely from Renogy, including a 20amp charge controller, two 1000Wh batteries, a 2000W inverter and a 440W solar panel. Total cost was around £850 including these items plus switches and fuses. I use it power the bike shed lights and power tools and to make ‘solar tea’ using a modestly rated travel kettle.
Off-grid expert advice and kit is available from the likes of Midsummer and Sunshine Solar.
Pros
Individual parts replaceable if they fail ie it is modular
Can scale up with more batteries, panels, higher rated controllers and inverters etc
Can be used when the sun doesn’t shine
Cons
Requires knowledge, DIY electrical skills and expert input
Probably won’t save you much (if any) money compared to the powerstation option
Not portable
Not as efficient as a solar direct to battery system (the first method described)
In other words, solar panels on your house roof which are then wired into the mains system (a so-called ‘grid-tied’ system) that can provide large amounts of solar power that comes straight out of your house’s plug sockets during bright conditions. These setups provide more than enough power for the typical house on a sunny summer day and are set up to be able to export electricity to the grid, for which you may get paid if you qualify under the Smart Export Guarantee.
I’ve had a 4kW system (that’s the peak nominal output rating) installed since 2015 and payments received for the electricity generated plus the cost of electricity saved means the system has now paid for itself, so electricity generated is effectively free, whatever it is used for, including charging of e-bikes.
For much of the year electricity generated is actually in excess of the house’s needs so I’ve also invested in a solar storage battery system. As electricity prices rise it becomes increasingly financially worthwhile to store the energy rather than export it so it can be used at night time and on days of heavy cloud.
My 10.2kWh capacity battery system can of course be used to recharge e-bikes and a new heavy duty cable means the 6kWh inverter it uses will also be quite capable of charging an electric car. A Solics solar diverter means it can also be used to heat hot water via the immersion tank element when there is surplus solar power.
If you get a smart meter and choose a suitable tariff from the likes of Octopus, you can also programme the system via an app to load up the battery with cheap off-peak electricity and save a bit of dosh that way.
The tricky bit is choosing from the many systems out there and getting good advice. I chose Ecoflow’s PowerOcean system on the basis they are a large and longstanding company offering a lengthy warranty and I also had good initial conversations with their recommended local installers, The Solar People.
You’ll also need a space to put the battery outside your house (rules now prohibit installing the battery inside a house). A garage or outbuilding is ideal but a sheltered spot on an outside wall is also possible. If you want to read about the ins and outs of solar storage batteries in more detail A to B issue 143 has a great article.
Solar installation costs have tumbled over the last decade, driven largely by a fall in prices for solar panels and seem to have bottomed out at around £5,000 for a 4kW system. My recently installed Powerocean solar battery from Ecoflow was very competitively priced at around £5,300 including installation and comes with a 15-year manufacturer’s warranty. It’s probably most economical to get a solar panel and battery system fitted all at once, if that’s the route you are likely to ultimately go down anyhow.
Pros
A cost-effective system given that you can power a lot things with, not just e-bikes!
Add in a solar storage battery to make the most use of long sunny days and store cheap electricity at off-peak hours.
Cons
This is undoubtedly expensive kit – but in the long run, just like a high quality e-bike, it can save you money
It remains to be seen if e-bike companies themselves embrace solar power themselves to a much greater extent than they have already – at present, offerings are limited to the commercial sphere and come from the likes of Solarcycle and Sunrider. But my own experiments have convinced me that, with advances in solar tech and falling prices, portable e-bike solar charging could well be offered alongside an e-bike purchase in the not too distant future. Such ventures currently seem confined to the likes of US’s Mokwheel at present but slicker and lighter systems are surely possible.
Further reading: Will there ever be a true solar power fed e-bike?
Richard Peace has almost certainly ridden and reviewed more electric bikes than anyone in the UK making him uniquely qualified to tackle reviews for Cycling Electric.
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Copyright © Diamond Publishing 2023. All rights reserved. Metropolis International Group Limited, 10th Floor, Southern House, Wellesley Grove, Croydon, CR0 1XG. Registered in England. Company No. 04611236
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