Proterra Energy was formed in 2012 with a grand plan to turn water into electricity, and that is what we have been doing for the last nine years, though more recently with a widening approach to include the sun and wind.  However, water is primarily what we deal with.

Our first hydro scheme installation was reusing old fish farm hatchery infrastructure to generate electricity through low head Pico turbines.  It powered the estate manager’s house and not much else but was a great example of how water flowing through an overflow pipe could be repurposed.

Fast forward nine years and we have over 150 projects under our belt ranging from feasibility through installation and onto operation and maintenance.  The smallest scheme is a 250W off-grid system that powers a set of electric gates and lights on a holiday park, up to penstock inspections on a 1.5MW scheme.   We have over 65 schemes that we provide O&M support for across Scotland – some from the 1930s and many installed between 2015 and 2018, a legacy of the gold rush that was the final years of the Feed in Tariff (FIT) in the UK.

Since the closure of the FIT scheme, our builds have dropped considerably as it has for most others in our industry.  Many companies have reverted to what they used to do before the FITs and unfortunately some have closed.  Proterra has been somewhat protected from this because early on we diversified into the maintenance of the schemes that we were installing and as numbers grew, we picked up other schemes that were installed by other firms that came to the Highlands of Scotland (temporarily) to join the game.  

We have also specialised in off-grid systems. Our first was installed in 2014 with 12 more since then.  There are different drivers for an off-grid customer and making sure the generation is matched with demand (or vice versa) is an important aspect of the design.  We have built some systems in some quite extraordinary places.

The outcome or spinoffs from this work has been twofold for us.


In 2016, whilst working on a remote intake construction, we wondered how we might power our site without the need for a generator and the constant ferrying of fuel.  From there was born the idea of a mobile micro hydro scheme which we called HydroTrailer.  It is pretty much what is says on the tin, a 3kW off-grid hydro scheme in a trailer.  From intake to outfall and electrical supply it all comes packaged in a small trailer, weighing around 500kg and takes an hour or so for two people to set up.

Initially our thinking was that it was as a replacement for a site generator but during visits to Chile where we were investigating the potential to install farm-scale hydro, it became clear that small remote communities could benefit from something like HydroTrailer.

We had been working with a company that supported a charity in Malawi and, coupled with our childhood experiences of growing up in Papua New Guinea, we recognised that communities in developing countries could be the main market for HydroTrailer.  Our research showed that aid funded micro hydro in developing countries was not new. It had been on the go since the 1980s but there were challenges. These included:

  • The complexity of the schemes.
  • How they operated after the installers left. 
  • The difficulty and cost in carrying out repairs.
  • The intermittency of generation.  

We have tried to design this out of HydroTrailer.  There are two red switches, one turns on the water and the other turns on the electricity.  The penstock is repairable, a leak can be fixed with a sharp knife and a screwdriver in about 20 minutes.  The batteries that provide the storage are not the latest lithium ion with inbuilt BMU and ethernet connectivity, rather they are lead acid batteries that can, if required, be swapped out with truck batteries from a local garage in about 30 minutes.   

As we heard from an old hand in these circles, “the first kW is worth far more than the 10 that follow it”.   This is a mantra we have tried to follow and is never truer in a time when an LED light bulb uses only 5W.

In 2019 we worked with a charity in Malawi to set up a trial of HydroTrailer in a village with no power.  It went really well. However, as any hydro installer will have experienced, when we got there we found that the hill wasn’t as steep and there was less water than they said! But the flexibility of HydroTrailer shone through. 

We released it from customs on its pallet and within 20 minutes it was road ready and on site about two hours’ drive from Blantyre the same morning.  We stopped on the way and bought batteries from a truck stop and fitted them on site and for the remainder of the trip it provided lighting and phone charging to houses in the village through a donated distribution network consisting of extension leads and portable lights.

On the back of this we pushed the commercialisation. The trailer is ready to go but we have found accessing the aid market (where we think our best opportunity is) very difficult.  As funding reduces, the competition increases, and we very much understand we are just one company in a queue with the next “best thing”.   However, we know ours is the next “best thing”! 

Unfortunately, then Covid hit with all its challenges and we, like many firms, were forced to redirect efforts to the day-to-day business.  We lost some staff to the ambulance service and companies making sanitiser.  Neil (my brother, the other company director) and I worked right through lockdown ensuring that the hydro schemes we serviced remained operational.

With hard work we have come out the other side, we have recruited again, and the business continues to grow.  We see changes in how people want to live their lives and as part of that, generate and use their electricity which brings us to the second spin-off of our off-grid work. 

Taking Off Grid, On Grid

There is increasing awareness of our energy, how we use it, and where it comes from.  Global warming is high on the agenda.   In the UK the FIT has at least met some of its objectives in that other forms of renewable generation have come down in price and are more widely accepted and understood.  One part of this system that has been discussed in recent editions of IWP&DC that isn’t so well understood by those not within the immediate industry (ie customers) is battery storage.  

We have been working with battery storage as part of our renewable installations since 2014.  Whilst many of our off-grid sites started out as hydro with battery storage we have upgraded them to hybrid systems with solar and in some cases micro wind, almost eliminating reliance on fossil fuel back up.

We are now installing grid connected hybrid solar battery systems.  We work with customers to understand their current (and future) electricity consumption and design the right system around that, as we would do for an off-grid system. 

We recognise that the big energy hitters will be in pumped storage hydro and offshore wind, but we firmly believe that dispersed generation also has an important role to play in rural regions.  It helps to answer questions like “How much energy is lost in transmission?” or “How does the existing grid support the growing demand from electric vehicles or electrical heating?”

Moving Forward

In a nation once dubbed by its politicians as ‘a hydro nation’, it is disappointing to find that though there are many technically feasible micro hydro sites, without FITs they struggle to be financially developed.  Hydro is a mature technology and even with the support of FITs was never going to reduce in price like others.  

However, as with much bigger pumped storage hydro schemes, there are ways that governments can encourage future installations.  Existing support mechanisms could be made simpler and less disjointed.  Consenting could be rationalised using the learning we have from installations over the past ten years.  This would significantly de-risk installations and make them potentially more affordable.  

One thing that seems certain is that we cannot afford to discount one of the earth’s biggest renewable contributors in our quest for decarbonisation.


For more information, or for those who might wish to partner with Proterra Energy and work on helping to get HydroTrailer to end users, email: