Renewable Desalination
We engineer solar-powered seawater reverse osmosis that follows cheap, clean power — turning an inexhaustible resource into fresh water, and a rigid load into flexible demand response.
The case
Freshwater demand is on track to outrun supply by around 40% before 2030. Conservation and reuse are essential — but they redistribute a shrinking pool. Only one source is truly drought-proof and effectively inexhaustible.
That source is the sea. Reverse osmosis can already pull fresh water from it near the efficiency limits set by physics. The catch has always been energy: the best desalination plants still demand enormous power — historically fossil power — putting water security on a collision course with the climate.
Renewable desalination dissolves that trade-off. Run the membranes on sunlight, and an inexhaustible resource becomes clean water with no operating emissions.
projected gap between global freshwater demand and supply by 2030
World Economic Forum / 2030 Water Resources Groupof Earth's water is seawater — drought-proof and effectively inexhaustible
Jones et al., Science of the Total Environment; compiled by Wikipediaenergy for modern seawater reverse osmosis — down from 20–30 kWh/m³ in the 1970s
Jones et al., Science of the Total Environment; compiled by Wikipedia“Seawater is the only source of fresh water that is drought-proof and inexhaustible.”
— Renewable Desalination
What changed
For decades, solar desalination was an engineer's dream priced out of reach. Then four cost curves bent at once — and the dream became the obvious answer.
Global weighted-average cost of utility-scale solar power, 2010–2024. What made emission-free desalination inevitable wasn't the membrane — it was the price of a solar watt.
Source: International Renewable Energy Agency (IRENA), 2025. Endpoints exact; interim years approximate the published curve.
| Year | USD per kWh |
|---|---|
| 2010 | 0.460 |
| 2013 | 0.240 |
| 2015 | 0.130 |
| 2018 | 0.075 |
| 2020 | 0.056 |
| 2022 | 0.049 |
| 2024 | 0.043 |
Utility-scale solar's total installed cost fell 87% between 2010 and 2024. Photovoltaic electricity now averages $0.043/kWh — about 41% cheaper than the lowest-cost fossil alternative.
International Renewable Energy Agency (IRENA) ↗Lead-acid batteries once accounted for more than 60% of the cost of off-grid solar desalination. Collapsing storage prices are making autonomous, around-the-clock installations viable in far more places.
International Renewable Energy Agency (IRENA) ↗RO is a mature technology operating near the efficiency limits set by thermodynamics — roughly 3 kWh/m³ today against a ~1 kWh/m³ floor. Further gains are incremental; the leverage has moved to the energy source.
Elimelech & Phillip, Science ↗Renewables are cheap but variable, and grids are slow to adapt. Desalination that can ramp with supply turns a problem into a solution: water is easy to store, so it becomes an ideal flexible, sacrificial load.
Council on Foreign Relations ↗The insight
A conventional plant demands the same power around the clock — exactly the wrong thing for a grid running on variable solar and wind. Our founding white paper proposes the opposite: replace one large pressure center with many small, fully-integrated modules, and automate how many run against real-time energy prices. Production rises when clean power is cheap and abundant, and eases off when the grid is strained.
| Hour | Price | Output |
|---|---|---|
| 0 | 46 | 28 |
| 1 | 44 | 30 |
| 2 | 42 | 30 |
| 3 | 42 | 28 |
| 4 | 45 | 26 |
| 5 | 52 | 24 |
| 6 | 64 | 18 |
| 7 | 86 | 10 |
| 8 | 96 | 12 |
| 9 | 72 | 38 |
| 10 | 46 | 72 |
| 11 | 30 | 90 |
| 12 | 22 | 100 |
| 13 | 20 | 100 |
| 14 | 25 | 94 |
| 15 | 36 | 80 |
| 16 | 56 | 52 |
| 17 | 82 | 22 |
| 18 | 100 | 9 |
| 19 | 95 | 11 |
| 20 | 80 | 20 |
| 21 | 66 | 30 |
| 22 | 56 | 34 |
| 23 | 50 | 30 |
Energy to make one cubic meter of fresh seawater, by era. Efficiency fell roughly 8-fold since the 1970s and now hovers near the ~1 kWh/m³ thermodynamic minimum — so the last big lever left is the source of the electricity.
Sources: Jones et al., Science of the Total Environment; compiled by Wikipedia; thermodynamic minimum per Elimelech & Phillip, Science, 2011.
| Era | kWh/m³ |
|---|---|
| 1970s | 25 |
| 1990s | 6 |
| 2010s | 3.5 |
| Today | 3 |
| Limit | 1 |
The engineering
Because RO already runs near its thermodynamic floor, we put our engineering where the leverage actually is: matching the desalination process to variable solar energy, and recovering every joule the brine still carries.
Membrane-based pretreatment (0.03-micron ultrafiltration) protects and extends the life of the RO components, and allows brine streams to be blended — significantly reducing the salinity of what returns to the sea.
Unique to this application, the variable frequency drives accept DC current directly from the solar array and batteries — eliminating expensive inverters and creating a naturally flexible, dispatchable load.
The most efficient positive-displacement high-pressure pump available — light, low-maintenance, and well matched to variable solar input.
An axial-piston motor recovers the pressure still held in the brine stream after desalination and applies it directly to the torque of the pump shaft — one of the first uses of paired APP/APM energy recovery.
A purely mechanical process that pushes fresh water through a semi-permeable membrane while the cross-flow of brine carries dissolved solids away — no heat, no phase change.
Systems & pilots
One design language, three scales — from a single home off the grid to a city on the grid. Small, fully integrated modules combine to reach any capacity.
Photovoltaic Seawater Reverse Osmosis Module
A fully integrated, off-grid 3 hp PV-SWRO module built around paired axial-piston pump and motor (APP/APM) for high pressure and energy recovery. The pilot runs three modules sharing a beach well, ultrafiltration, storage, solar array and battery bank.
Photovoltaic Seawater Reverse Osmosis Module
The 30 hp sibling of the T-1 — the same PV-SWRO architecture and APP/APM energy recovery, scaled up for large hotels, communities and small cities. Modules combine to reach the capacity a site needs.
White paper · grid-connected concept
A grid-connected concept: replace one large pressure center with a multitude of small, fully integrated RO modules, then automate how many run against real-time energy prices. Cheap power lowers operating cost — and the plant delivers valuable demand response to operators balancing wind and solar.
Proof on the Sea of Cortez
Our research facility in Baja California Sur runs on a 60 kW solar array that powers the lab, the shop, irrigation, and two autonomous seawater desalination systems. Over more than a decade, the pilot has produced over 18 million gallons of fresh water — 68,000 m³ — using nothing but sunlight, and grown more than 800 trees from bare desert.
of fresh water produced on solar energy alone (68,000 m³) over the pilot's first 12+ years
grown from bare desert using desalinated water
array powering the Sea of Cortez research facility
greenhouse-gas emissions in operation — sunlight in, water out
Questions, answered
Photovoltaic panels power high-pressure pumps that push seawater through reverse-osmosis membranes. Fresh water passes through; concentrated brine is returned to the sea. Our design drives the pumps directly from DC solar and recovers pressure from the brine stream, so the whole process runs on sunlight with no fuel and no operating emissions.
Modern seawater RO uses roughly 3 kWh per cubic meter of fresh water — down from 20–30 kWh/m³ in the 1970s — approaching a thermodynamic floor of about 1 kWh/m³. Because efficiency gains are now incremental, the biggest lever for cutting emissions is the source of the electricity.
Yes. We have operated two autonomous PV-SWRO labs on the Sea of Cortez for over a decade, together producing more than 18 million gallons of fresh water (68,000 m³) using only solar energy. Water is easy to store, so production can be shifted to sunny hours and drawn on later.
Its two concerns are energy use and brine discharge. We address both: powering the process with solar removes the operating emissions, and membrane pretreatment lets brine streams be blended to lower the salinity returned to the sea.
It is a grid-connected design that splits a desalination plant into many small modules and automates how many run based on real-time electricity prices. The plant produces more when clean power is cheap and abundant, giving grid operators a flexible load that helps them absorb more wind and solar.
Renewable Desalination is a research-and-development effort that has pioneered photovoltaic seawater reverse osmosis since the late 1990s. Its R&D facility in Baja California Sur, Mexico runs on a 60 kW solar array and has turned desalinated seawater into an orchard of more than 800 trees where only cactus grew before.
Let's build it
Whether you're planning an off-grid installation, a community system, or grid-scale demand response — let's talk about what solar desalination can do for your site.