An edited version of this article on hybrid renewable systems was submitted to the International Journal on Hydropower & Dams in May 2026.
Hydropower: A Reliable Partner for Hybrid Renewable Energy
A few years ago, we powered a small village in Malawi with our Offgrid HydroTrailer. The project and visit were a great success, but whilst there something else struck me.
The primary use of power was to provide lighting in homes that had no lights, but the second most important thing for the people was to use power to charge mobile phones. Being there I noticed how many people had mobile phones as there was no landline network. As a developing nation they had moved straight from no phones to mobile phones, not a network of cables crisscrossing the country with the associated undertaking of installation, or the resulting environmental impact.
Drawing a parallel with power distribution, in the UK and Scotland, we developed progressively from the very earliest sites with local power to a national grid network. We now have the challenge, and significant undertaking, of upgrading this network as our energy demands and transmission requirements increase. The hardest part of this is often not replacing the cables, but the scale of the infrastructure projects required to enable the works, issues surrounding land use, access and wayleaves, environmental impact and the cumulative effect these have on overall delivery costs.
However, there is a different way, one that we have seen in our work over the last couple of years. We can, and have, provided localised energy using hybrid renewable energy systems to generate power in an ‘off-grid’ capacity. Off-grid is traditionally seen as the preserve of the most remote places, bothies in the hills, but when weighed against the costs and challenges of extending the distribution network, the increasing capability of renewable energy systems and falling technology prices make returning to local off-grid generation an increasingly viable option.
The effectiveness of hybrid renewable energy systems
Between summer 2024 and 2025 we undertook a project to do just that, and is wasn’t for a bothy in the hills…
Scaliscro Estate on the Isle of Lewis, off the West Coast of Scotland, recently acquired by a new owner, was undergoing significant redevelopment. The main lodge was replaced, new houses were built for staff, workshops were brought back into service and a new refrigerated larder installed. We were approached to look at repurposing abandoned fish hatchery infrastructure to provide hydropower.
It soon became clear that the increased electrical demands of the Estate, driven by legislation surrounding renewable heat and EV charging requirements, meant that the 3km spur off the main network distribution line would need to be upgraded to provide the capacity required.
The cost of that upgrade started out as a 7 figure sum, a threat to the whole project. Given our off-grid system background, the Client tasked us with finding a solution. And we did; a hybrid renewable system feeding hydro and solar generation into a 150kW off-grid system with ~380kWhr of battery storage. A back-up generator was installed for low generation periods. The whole system was cheaper than the cost to upgrade the grid and allowed the Client to remove the power lines running through their property.
Hydro power is provided by a Turgo turbine with a design flow of 65l/s, fed from the old hatchery weir on a loch above the Estate. In addition to battery storage, drawing down the loch during dry periods (as agreed with the local environment agency) gives the system an additional water ‘battery’ reserve of approximately 4-5 days (a benefit over a run-of-river system).
The hydro system is coupled with two 25kW solar arrays, one roof mounted and the other ground mounted. Together they provide a year-round renewable energy resource. The hydro has already outperformed its baseline annual generation estimate, by month 10. Which is just as well because the Estate has exceeded its consumption estimates too!
The complete renewable and off-grid system has been fully operational for almost a year now; the off-grid system is approaching the end of its second year as it was installed first. In this time, the Client has had fewer (no!) outages caused by a failure of the ‘grid’. Those that have occurred were due to localised consumer related issues: water in domestic lighting, use of non-protected mobile power tools, etc. In other words, the system has proved to be more reliable than the main network 3km away. It has not been totally perfect, but the resilience of the system has meant that it has continued to supply power throughout these periods.
Developing reliable off-grid and hybrid renewable systems
We (people) have adopted elements of off-grid protection and local generation in many ways and in many places. Returning to Africa, the prevalence of UPS-style systems in homes and businesses in South Africa to manage rolling blackouts is a good example.
We (Proterra Energy) are building off-grid capable systems across the Highlands of Scotland, on grid connected sites where properties are subject to regular power outages and / or where Clients want peace of mind and energy security. We also regularly offer off-grid solutions to customers building new properties where obtaining a new grid connection is not possible or cost prohibitive.
Where hydro resources are available, their reliable nature means that micro hydro often forms the backbone of renewable energy systems. When integrated with solar generation, battery storage, thermal diversion capability and back-up generator provision, hybrid off-grid systems compete with and overcome the challenges of grid supply, in the same way that mobile phones have overcome challenges in communication.
