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Hybrid Solar-Geothermal Sites Mapped in Cold Northern Iran
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A GIS study published in the journal Geothermal Energy has identified 1,155.25 square kilometres across three cold provinces of northwestern Iran as suitable for hybrid solar-geothermal plants. That land is 1.15 percent of West Azerbaijan, East Azerbaijan and Ardabil combined. The authors put its technical generation potential at 3,302,987,455 megawatt-hours a year. East Azerbaijan scored highest for operational potential, and Ardabil showed the lowest combined output. The five researchers, with Younes Noorollahi as first author, ranked the land by weighting 17 data layers through the Analytic Hierarchy Process. The figures describe what the chosen criteria allow, not projects in development. No site has been surveyed or permitted on the strength of the mapping, which appeared on 21 August 2026.
Key takeaways
- Suitable land: The Noorollahi team classed 1,155.25 square kilometres, or 1.15 percent of West Azerbaijan, East Azerbaijan and Ardabil, as suitable for hybrid solar-geothermal plants.
- Generation ceiling: The study estimates a technical potential of 3,302,987,455 megawatt-hours a year for the three provinces together. This is a modelled figure, not output measured at any operating plant.
- Provincial split: East Azerbaijan ranked highest for operational potential for hybrid generation, while Ardabil had the lowest solar-geothermal output of the three provinces.
- Method: The ranking combined 17 economic, technical, environmental and geological data layers in a GIS model weighted with the Analytic Hierarchy Process.
Table of contents
Where Northern Iran's Hybrid Plant Land Lies
The study covers West Azerbaijan, East Azerbaijan and Ardabil, three provinces in the cold northwest of Iran. Across their combined territory, the model flagged 1,155.25 square kilometres as fit for plants that pair solar and geothermal generation. That is 1.15 percent of the land. On that share, the three provinces together cover roughly 100,000 square kilometres.
The provinces did not perform equally. East Azerbaijan came out on top for operational potential for hybrid generation. Ardabil produced the smallest solar-geothermal output of the three. For anyone deciding where to spend the next round of survey money, that ordering is the most actionable result in the paper.
The published summary names the two ends of the ranking and stops there. West Azerbaijan's individual score is not broken out, so its position between the other two cannot be read from the released figures. The authors argue that this cold corner of Iran suits hybrid plants because sunshine and underground heat can complement each other there.
How 17 Data Layers Became One Suitability Map
A geographic information system, or GIS, stores mapped data as stacked layers so that every patch of ground can be scored against many criteria at once. The team fed 17 such layers into its model, grouped under four headings: economic, technical, environmental and geological.
The Analytic Hierarchy Process sits on top of that stack. It is a decision method in which each criterion receives a relative weight and the weighted results are combined into a single score. Land that does well on the heavily weighted factors rises to the top of the ranking.
The authors claim their main advance is evaluating solar and geothermal resources together in cold climates. They say their model also folds in technical and operational factors that earlier siting work mostly left out. They call the resulting structure robust and efficient. Those are the authors' judgments of their own method, and the published summary does not test them against an independent assessment.
Why 3.3 Billion Megawatt-Hours Is a Ceiling, Not a Forecast
The land figure is a product of the criteria and weights the team selected. None of the 1,155.25 square kilometres has been surveyed, permitted or set aside for a power plant because of this work. Change the weights and the map changes with it.
The energy figure needs the same care. The 3,302,987,455 megawatt-hours a year, roughly 3.3 billion, is a technical potential for the three provinces together. It is calculated from the assessment rather than measured at any plant running today. Spread across the suitable land, it implies about 2.86 million megawatt-hours a year from each square kilometre. That ratio is worth testing against real output once any plant operates.
What an actual project could deliver depends on three things the model cannot settle. The first is which technologies are installed. The second is whether drilling confirms the geothermal resource at each site. The third is what it costs to connect to the grid. Each of these could shrink the usable share of the mapped area.
What the Map Offers Planners in Cold Regions
The authors argue that pairing the two sources could cover local demand, especially where conventional electricity infrastructure is thin. That is a statement about potential. The study does not report any project being planned at the mapped sites.
They also aim the work at policymakers and renewable-energy stakeholders. They present it as a framework for optimising combined solar-geothermal projects in cold regions. For provincial planners, its practical value is a shortlist: East Azerbaijan first for operational potential, plus a map showing where detailed and costly site investigation could begin.
The paper is open access, so its full maps and weightings are available to anyone who wants to check the assumptions. It can be found under DOI 10.1186/s40517-026-00401-9. By late October 2026 it had recorded two citations, a modest count that leaves the method largely untested by other groups so far.
| Measure | Value | What it represents |
|---|---|---|
| Provinces covered | 3 | West Azerbaijan, East Azerbaijan, Ardabil |
| Data layers | 17 | Economic, technical, environmental, geological |
| Suitable area | 1,155.25 sq km | Land passing the weighted criteria |
| Share of total area | 1.15 percent | Of the three provinces combined |
| Technical potential | 3,302,987,455 MWh a year | Modelled, not measured |
| Highest operational potential | East Azerbaijan | Provincial ranking |
| Lowest combined output | Ardabil | Provincial ranking |
The case for and against the mapped sites
The case for
- Weighting 17 layers across four criteria groups narrows a large region to a small, ranked set of candidate sites before costly fieldwork begins.
- East Azerbaijan's top operational score gives planners a clear first province to investigate.
- The authors argue hybrid plants could serve areas with thin electricity infrastructure, where local generation matters most.
- Open-access publication lets other teams check and reuse the weightings.
The case against
- The suitable area depends on weights the authors chose; different weights would yield a different map.
- The 3,302,987,455 MWh estimate is technical potential, not output from any operating plant.
- Geothermal resources at the mapped sites remain unconfirmed by drilling.
- Grid connection costs and technology choices could cut the share of mapped land that proves viable.
What to be careful about
- Geothermal resources at the 1,155.25 square kilometres of mapped land have not been confirmed, so some sites may fail once drilling begins.
- The suitability ranking is sensitive to the Analytic Hierarchy Process weights, and those weights reflect the authors' judgments.
- Grid connection costs in areas with limited infrastructure could make technically suitable sites uneconomic.
- With two citations so far, the framework has had little independent scrutiny.
The bottom line
The Noorollahi team has given northwestern Iran a ranked starting point for hybrid power: 1,155.25 square kilometres where sun and underground heat score well enough together to count as suitable, with East Azerbaijan at the head of the list. That is useful work, and it is preliminary work. The 3,302,987,455 megawatt-hour estimate is a technical ceiling built from chosen weights, not a measured yield. The geothermal resource beneath each mapped parcel is still unconfirmed. The real test of the framework is whether its rankings hold up once someone drills. Until a developer or provincial authority takes a mapped site to survey, the study remains a well-structured hypothesis about where hybrid plants in cold regions belong.
What to watch
- Watch for a follow-up study or field survey that tests geothermal resources at the East Azerbaijan sites the model ranked highest; no date has been set.
- Watch whether any provincial authority or developer in West Azerbaijan, East Azerbaijan or Ardabil proposes a hybrid solar-geothermal plant on land the study mapped as suitable; no timetable has been announced.
- Watch the paper's citation count beyond the two recorded by October 2026 as a sign of whether other research groups adopt or challenge the 17-layer framework; no date applies.
Frequently asked questions
Who wrote the northern Iran solar-geothermal siting study, and is it free to read?
The authors are Younes Noorollahi, Mohammad Zare, Mohammadali Allahrabbi Shirazi, Hossein Yousefi and Amir Naseri. The paper appeared in the journal Geothermal Energy on 21 August 2026 and is open access under DOI 10.1186/s40517-026-00401-9.
Why look for hybrid solar-geothermal sites in cold provinces?
The authors argue that solar radiation and geothermal heat can complement each other in cold regions such as West Azerbaijan, East Azerbaijan and Ardabil. They also say technical and operational questions about hybrid systems in cold climates have received little attention in earlier siting studies.
How does West Azerbaijan rank for hybrid solar-geothermal plants?
The published summary does not give West Azerbaijan a separate score. It names only East Azerbaijan as highest for operational potential and Ardabil as lowest for combined output. West Azerbaijan's land is included in the 1,155.25 square kilometres judged suitable across all three provinces.
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