ALTO Solution · Concentrating solar heat for industry

Frequently asked questions

ALTO & its plants

Three orders of magnitude to compare against your current benchmarks.

Decarbonation: up to 100% of the substituted share, which can represent 10 to 90% of your thermal needs depending on your consumption profile, your location and the storage sizing. Try it on our simulator and eligibility guide.

ALTO heat price: 30 to 70 €/MWh on a long-term contract, stabilised over 20-25 years. The range depends on your location (DNI), your hourly profile, storage, technical configuration, and several financial parameters.

Land footprint: 5,000 m² of land i.e. 2,500 m² of collectors for 1.5 MW, so as not to create inter-row shading. A 10 MW plant reaches 30-40 GWh/year depending on location, comparable to the consumption of a mid-sized agri-food plant.

Three main criteria determine a site’s eligibility:

Process temperature: your needs must fall between 100 and 500°C - the range covered by ALTO’s solar concentration technology.

Thermal power: your continuous need must be between 1.5 and 30 thermal MW. Below that, economies of scale aren’t sufficient; above, contact us so we can explore a configuration tailored to your site together.

Solar resource and available area: the site must have an adjacent plot of at least 5,000 m² (corresponding to a 1.5 MW plant) and a sufficient direct solar irradiance (DNI) - typically above 1,200 kWh/m²/year.

These criteria are automatically analysed in our eligibility module - test your site in 3 minutes.

ALTO designs, structures financing, manages construction and operates concentrating solar heat plants for industrial companies whose processes require heat between 100°C and 500°C.

The model is service-based: you only pay for the heat actually delivered, at a stable price guaranteed over 20 to 25 years. No upfront investment, no operating costs - ALTO finances, installs, maintains and insures the installation for the entire contract duration.

In practice: a plant is installed on your site - or nearby, connected to your existing heat network, and produces decarbonised heat (~20 gCO₂/kWh) with a cost independent of natural gas and CO₂ price swings.

ALTO technology stands out on several structural points compared with conventional troughs:

CAPEX reduced by ~30% thanks to innovations on the structure and foundations.

Wind resistance 3× higher (135 km/h vs 45 km/h) - a critical criterion for long-term reliability under real-world conditions.

Mirror bending at ambient temperature: better optical quality, without the industrial constraints of hot bending or its associated costs.

Non-buried external foundations: no soil artificialisation or sealing, plant fully relocatable if needed.

Full dismantling at end of life with concrete reuse in a circular economy approach.

Discover the Technology section for more details.

The plant is connected to your plant’s existing thermal network - usually via a heat exchanger on the heat transfer fluid side, or directly to the steam network after a solar evaporator for steam processes - at the temperature and pressure already used by your processes, without modifying your downstream installation. The collector field is installed on a flat, clear outdoor surface and linked to your boiler room by an insulated transfer loop.

The integration runs in parallel with your current heat source (gas boiler, steam network), which remains in place as backup. ALTO carries out an upfront detailed thermal audit of your existing equipment (exchangers, pumps, control systems) to define the optimal connection point. In almost all cases, no modification of the downstream process is required.

The heat produced by ALTO technology emits about 20 gCO₂ per thermal kWh delivered (embedded energy of equipment over their lifetime), i.e. 12 times less than natural gas (≈ 240 gCO₂/kWh). For a site consuming 5 GWh/year of heat, switching to ALTO represents a reduction of about 1,360 tCO₂ per year (net LCA, after 90% burner efficiency and LHV/HHV ratio 0.9) - i.e. the annual footprint of about 680 ICE cars (ref. ADEME: ~2 tCO₂/car/year). This reduction is certifiable and translates into a direct decrease of your Scope 1 in your CSR reports.

ALTO is in commercial development phase in France and Spain. ALTO’s founders, Mauro and Mehdi, previously developed and built industrial concentrating solar heat plants in Morocco. This direct field experience is at the heart of ALTO’s offer design: every technological and contractual choice flows from it.

The GHG Protocol distinguishes three industrial emission scopes:

Scope 1 - direct emissions from sources you control (on-site combustion: boilers, furnaces, vehicles).
Scope 2 - indirect emissions linked to the energy you purchase (electricity, steam, heat, cooling).
Scope 3 - other indirect emissions across your value chain (purchased goods and services, transport, use and end-of-life...).

In our model, you no longer operate combustion on site for this thermal need: your associated Scope 1 disappears. The heat delivered by ALTO becomes your Scope 2 (purchased energy) with a near-zero carbon intensity - concentrating solar emits no direct CO₂ in use. The embedded energy of the equipment (~20 gCO₂/kWh over full lifecycle) can be reported under Scope 3 category 1 for a detailed value-chain assessment, i.e. 12 times less than the total LCA intensity of a gas boiler (~240 gCO₂/kWh, of which ~200 gCO₂/kWh in Scope 1 direct combustion and ~40 gCO₂/kWh in upstream Scope 3 - extraction, methane leaks, transport, refining).

Solar production is intermittent by nature - it’s a reality the system is designed to handle, not ignore. Two mechanisms combine:

Thermal storage absorbs hourly and daily variations (several hours of autonomy depending on sizing). Your existing heat source (gas boiler, steam network) remains in parallel and automatically takes over at night or during prolonged very cloudy days - the process experiences no discontinuity.

The plant is sized from the site’s historical irradiance data (typical meteorological year, 15-20 years of measurements). Over a full year, it typically covers 10 to 90% of thermal needs depending on the site and latitude - the remainder being covered by the backup.

The choice of fluid depends on the target temperature and application.

Pressurised water - up to 220°C under pressure. Natural fluid, inexpensive, compatible with most existing process networks.
Pros: universal, economical, compatible with existing installations, storage via insulated pressurised tank.
Cons: high pressure beyond 220°C (HSE constraints).

Thermal oil (Therminol, Dowtherm…) - from 150°C to 400°C. Liquid at ambient temperature, no high pressure, ideal for storage-based systems.
Pros: wide temperature range without high pressure, good heat capacity, compatible with hot/cold tank storage.
Cons: fluid cost, progressive degradation (periodic replacement), end-of-life waste management.

Nitrogen - gaseous fluid for temperatures > 400°C or very specific configurations. Still an emerging technology in concentrating solar though proven in other industrial fields.
Pros: inert, no risk of product contamination, very high temperatures achievable.
Cons: low energy density, expensive compressors, high electrical consumption. Suited to very specific cases.

Thermal storage allows you to decouple solar production from industrial consumption - to cover cloud passes, continue into the evening, or smooth power demand. The storage technology is chosen consistently with the heat transfer fluid:

Storage of the fluid itself (hot/cold tanks) - the most widespread solution with thermal oils. Two insulated tanks (one hot ~380°C, one cold ~290°C) provide several hours of autonomy with no complex mechanical part.

Pressurised water thermocline storage - a single stratified tank maintains water under pressure between ~90°C and ~220°C. The hot zone in the upper part is drawn off in priority; the cold zone in the lower part recharges progressively as the exchanger returns. Compact and economical solution, well suited to pressurised water systems.

Latent heat storage (PCM) - phase-change materials (salts, alloys) for high energy densities in a reduced volume. Technology in progressive industrial deployment.

Air-on-rock-bed storage - hot air produced by the solar field passes through a bed of rocks or granular materials that accumulate and release heat. Robust solution, with no pressurised fluid or chemical risk, suited to hot-air processes between 150°C and 500°C.

In all cases, storage capacity is sized according to your real consumption profile - it can go up to 72 h, but is generally in the 1 to 8 hour range of solar production.

The ALTO plant is designed for a minimum lifespan of 25 to 30 years. Each component has its own trajectory:

Concrete structure: lifespan above 50 years, comparable to industrial building. No replacement planned.

Solar mirrors: 25-30 year lifespan with preventive maintenance. Very limited progressive optical degradation (1-2% per decade under typical conditions).

Absorber tubes: 25-30 year lifespan. Vacuum losses may require selective replacement over time.

Heat transfer fluid: lifespan varies by fluid (water no degradation, thermal oil partial replacement every 10-15 years depending on the thermal profile).

Pumps and tracker motors: preventive maintenance with occasional replacement depending on wear, covered by the ALTO contract.

Concentrating solar exists in four main architectures - the choice depends on the target temperature and scale.

Solar tower: hundreds of flat mirrors (heliostats) concentrate light onto a receiver at the top of a tower. Very high temperatures (>500°C) and large capacities (>50 MW). This is generally the preferred application for large-scale renewable electricity generation. Significant complexity and costs, not suited to common industrial needs, nor to constrained urban environments where building permits are compromised by urban planning regulations.

Linear Fresnel: flat linear mirrors concentrating onto a fixed tube. Simpler architecture, more wind-resistant, but optical efficiency 15 to 20% lower than parabolic mirrors - which requires a collector area 17 to 25% larger to produce the same amount of heat.

Dish: individual parabolas with point focus. Very high efficiency and potentially very high temperatures. But small units (a few kW) and high cost per kW - reserved for specific applications, not suited to industrial scale.

Parabolic mirrors (parabolic troughs, ALTO): this is the most mature and best-documented technology for the 100-400°C range; ALTO extends this range to 500°C thanks to an adapted heat transfer fluid (see our technology). This range covers 70% of industrial thermal needs. Good trade-off between efficiency / complexity / cost, with proven bankability across more than 40 years of commercial deployment worldwide.

ALTO focuses its innovations on the parabolic architecture to maximise competitiveness in the 1.5-30 MW industrial segment.

Industry & thermal landscape

More than half of the heat in the world is consumed in industry, and 70% of these industrial needs are below 500°C - the exact range covered by ALTO. (IEA Renewables 2022 Analysis · IEA SHC Task 64 Position Paper, 2024)

The technical potential addressable by concentrating solar represents 1,850 TWh/year - i.e. 4% of the world’s industrial heat in the range covered by ALTO. (IEA SHC Task 64, 2024) To give a scale: 1 TWh/year represents about 50-100 ALTO plants of 5-10 MW - some 2 million m² of mirrors. The most intensive sectors and their process profiles are detailed in the next question and in the Applications section. The pace of execution is the only real limiting factor.

Heat represents ~74% of industry’s total energy consumption - vs ~26% for electricity. Our Applications section details the most common processes in our 100-500°C operating range.

Source: REN21 GSR 2025, based on IEA World Energy Balance 2025 · 2021 data

World industry consumes most of its energy in the form of heat - 73.8% of industrial final energy. The remaining 26% are non-thermal uses: motors, compressors, lighting, electrolysis.

Today, this heat remains massively fossil:

87.6% comes from fossil fuels (natural gas, coal, fuel oil) - mostly via direct combustion, the rest via fossil electricity or fossil district heat networks.

Only 12.4% comes from renewable sources, dominated by biomass (about 11% of total heat); solar thermal and geothermal together represent less than 1%.

On the delivery side, electricity currently supplies 4% of industrial heat (of which 1.3% is renewable electricity), and district heat networks deliver 8.5% - mostly fed by fossil sources.

Source: REN21 GSR 2025, Renewables in Industry Factsheet, IEA World Energy Balance 2022 data.

The industrial solar heat market (SHIP, Solar Heat for Industrial Processes) is in a phase of structural emergence: 1,315 installations recorded worldwide for a total capacity of 1 GW installed, against a technical potential estimated at 2,730 GW. The current penetration rate is 0.04% of the addressable potential - i.e. a near-untapped market.

This imbalance between potential and deployment is explained by the relative youth of the industry, the historical weakness of gas prices, and the absence of turnkey solutions allowing an industrial company to delegate the management of a non-core energy asset. This is precisely ALTO’s positioning: remove these barriers through a long-term heat purchase contract, with no investment or technical skill required.

Sources: IEA SHC Solar Heat Worldwide 2024 / Solrico, February 2025 · IEA SHC Task 64 Position Paper, January 2024

Two indicators shape the economic environment of fossil industrial heat:

Natural gas - TTF

- €/MWh

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European reference price (Dutch hub) · Benchmark used for industrial supply contracts in Europe

Live price →

CO₂ - EU ETS (EUA)

- €/t

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European carbon allowance price (EU Emission Trading System) · Structurally raises the cost of fossil energy for industrial companies subject to the scheme

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Each solution has its area of relevance - ALTO doesn’t compete head-on with all of them:

Geothermal: ideal for low-temperature district heating networks (<150°C). Renewable and stable, but high CAPEX, dependent on local geological context, limited operating zones. High temperature only possible in volcanic zones.

Biogas: circular waste valorisation, local production, storable. But limited resource increasingly contested between uses (grid injection, mobility, industry) - growing tensions on supply. Cost indexed on natural gas for grid injection.

Biomass: high temperature achievable, renewable. But growing tensions on resources (material vs energy competition), complex supply logistics, fine particle emissions, and ongoing debate on the real sustainability of the forest sector. Wood-chip prices rising structurally. From a technical standpoint, the power output of an operating biomass boiler is also difficult to regulate - ramp-up and ramp-down are slow, which can be constraining for industrial processes with variable demand.

Gas: available everywhere, flexible, high temperature, existing infrastructure. But significant direct CO₂ emissions (~240 gCO₂/kWh), volatile prices structurally exposed to supply crises, growing exposure to carbon pricing (EU ETS), and an unfavourable regulatory trajectory in the context of industrial decarbonation.

ALTO complements this landscape: ~20 gCO₂/kWh full lifecycle (the lowest), 70% of industrial needs covered (100-500°C), stable and predictable price for 20 years, with no geological constraint or input dependency. Discover our technology.

Waste heat (or recovered heat) refers to heat from an industrial process that would be lost without valorisation - flue gases, vapours, hot effluents, thermal discharges. Recovering it to feed another process or a heat network is an energy efficiency step.

Pros: energy already available on site, low marginal cost if the exchange infrastructure allows it, no intermittency.

Limits: quantity limited by the resource available on site (often only 10-30% of total needs), generally low temperature (typically <200°C), thermal quality degraded compared with the primary source, and above all it doesn’t decarbonise the primary source - if your gas boiler produces 10 GWh and you recover 2 GWh as waste heat, you’re still burning the same amount of gas.

Complementarity with ALTO: waste heat recovery should be prioritised first (efficiency gain with no heavy investment). Once optimisation is done, concentrating solar heat substitutes the residual primary production, which typically remains the majority of needs - and that’s where it has the strongest carbon impact.

Yes. Several schemes can apply depending on the project configuration:

CEE (French Energy Saving Certificates): industrial solar heat installations are eligible for CEE certificates, valorisable directly or transferred to obligated parties.

French ADEME Heat Fund: national French grant dedicated to industrial renewable heat projects. CSH plants are explicitly eligible subject to size and use conditions.

European green taxonomy: investments in industrial solar heat meet the EU taxonomy criteria for sustainable activities - which facilitates access to green financing (green bonds, EIB or BPI subsidised loans).

Regional aid (France): several regions complement the national scheme. Région Sud (PACA) has launched an industrial solar heat plan with subsidies dedicated to CSH installations. Other regions (Occitanie, Nouvelle-Aquitaine) run regular calls for industrial renewables projects - ALTO monitors and applies to these schemes for each project.

Aid in Spain: the PERTE Agroalimentario programme and Next Generation EU funds (PRTR) finance industrial decarbonation, including solar heat. Autonomous communities (Andalucía, Cataluña, Valencia) offer complementary support via their regional energy agencies. ALTO supports its Spanish clients in identifying and structuring these applications.

In our model, ALTO structures and manages these schemes on behalf of the project - the industrial client has no administrative steps to carry out.

The 100-500°C range corresponds to the majority of industrial thermal needs - about 70% of the heat consumed in industry. This is the strategic segment covered by ALTO, between two zones dominated by other technologies:

Below 100°C: domain of heat pumps and flat-plate solar thermal. High heat-pump efficiency, but temperature-limited by physics (COP collapses above 80-120°C).

100-500°C: intermediate zone poorly covered by alternatives - too high for heat pumps, too low for direct electrification at acceptable cost. This is the core of industrial processes: drying, distillation, sterilisation, polymerisation, cooking, juice concentration, steam production. Concentrating solar heat (CSH) is the only renewable technology economically relevant across the full range.

Above 500°C: domain of high-temperature industries (metallurgy, glass, cement). Requires either more complex CSH technologies (solar tower), direct electrification via electric arc furnace, or green hydrogen.

The TTF is the wholesale price of natural gas, continuously quoted on the Dutch hub. But it’s only a fraction of the price actually paid by an industrial company. The ALTO simulator reconstructs the industrial pre-tax price in five components:

1. Wholesale price (hub) - TTF (Dutch hub), 12-month rolling average to smooth seasonal peaks. 2024 reference: ~35 €/MWh.

2. Commercial spread - gap between the commodity invoiced to industrial companies and the hub price. Covers supplier margin, structured product costs and market risk hedging. Typically 4-7 €/MWh, variable depending on site size and contract duration.

3. Transport - transport and distribution network tariffs, set by the national regulator (CRE). From 1.5 to 11 €/MWh depending on consumption.

4. Energy taxes - TICGN in France. From 4 to 25 €/MWh depending on the profile and applicable tax regime (standard rate or reduced large-consumer rate).

5. ETS surcharge - when the site is subject to the European Emissions Trading System, the EUA price applied to the natural gas emission factor (0.223 tCO₂/MWh = 0.201 LHV French ADEME Base Carbone / 0.90 standard boiler efficiency) typically adds 14-17 €/MWh at 2024-2025 prices. The simulator allows switching between ETS and non-ETS regimes depending on your situation.

In total, an industrial company pays an all-in pre-tax price that can reach 1.5 to 2.5 times the gross TTF price, depending on the country, the site size and exposure to the carbon market. A comparison based on TTF alone would structurally underestimate the actual gas cost - and therefore the potential saving with ALTO - by 25 to 50 €/MWh.

France-specific case - two methodological choices distinguish the simulator:

The commercial spread is set on the "large consumers" band (Eurostat I4, 3.95 €/MWh) regardless of consumption, because ALTO’s target sites have a flat 24/7 profile that doesn’t mobilise seasonal regulated storage (incorporated into Eurostat commodity).

Taxes use the official TICGN (17.16 €/MWh in 2025, French Customs Code) rather than aggregated Eurostat averages. An option allows switching to the reduced rate (1.52 €/MWh, article 265 nonies) for large energy-intensive consumers subject to the EU ETS.

See the detail of public sources used at the foot of the FAQ: Calibration sources.

Concentrating solar

CSH stands for Concentrating Solar Heat. It’s a technology that uses mirrors to concentrate direct solar radiation onto an absorber tube and produce heat at high temperatures - typically between 100°C and 500°C. Unlike photovoltaics, which produces electricity, CSH directly produces heat usable in industrial processes: steam, pressurised water, thermal fluid. To be distinguished from CSP (Concentrating Solar Power), which uses the same optical principle but to produce electricity via a steam turbine.

The principle rests on optical concentration: mirrors (called collectors or heliostats) track the sun’s path and redirect the radiation onto a focal point or line where an absorber tube is placed. The heat transfer fluid flowing in this tube rises in temperature. ALTO uses a parabolic trough collector architecture - the most mature and best-documented technology for industrial temperatures (100-400°C). The solar field is coupled with a heat exchanger or evaporator, depending on the configuration, which transfers heat to the existing industrial process network. How does the plant integrate with the process?

Both technologies capture solar energy but produce very different things.

Photovoltaics (PV): panels convert sunlight into electricity, with an average annual efficiency of ~15%. They work with direct as well as diffuse light (under cloudy skies, with reduced efficiency).

Concentrating solar heat (CSH): mirrors concentrate the direct radiation of the sun onto an absorber tube, heating a heat transfer fluid up to 500°C. Average annual thermal efficiency ~50% - three times higher than PV. The result is heat directly usable by industrial processes. Requires solar irradiation from 1,200 kWh/m²/year DNI (where can this level of irradiation be found?).

In short: PV = electrons (~15%), CSH = heat (~50%). For the same amount of energy produced, you’d need 3.3 times more PV panel area than CSH collector area (ratio 50/15). For an industrial company needing 300°C process heat, going through PV would also impose an electric→thermal conversion (losses, cost), whereas concentrating solar supplies heat directly.

Parabolic mirrors work via optical concentration: they precisely focus all incident rays onto an absorber tube - the focal line. This focusing is only possible for parallel rays arriving directly from the sun (DNI). Diffuse light - radiation scattered by clouds or the atmosphere - arrives from all directions and cannot be concentrated by a mirror. Conversely, photovoltaics, which converts each photon individually on the surface of a flat panel, harnesses both direct and diffuse light.

Consequence: concentrating solar is only relevant in regions with a strong direct component - typically from 1,200 kWh/m²/year of DNI. Below this threshold, energy output isn’t sufficient to allow full profitability of the plant.

Full substitution is technically possible but rarely economically optimal. Three reasons:

Seasonal variability: even in high-DNI zones, winter production remains lower than summer production. Sizing to cover 100% in winter implies massive oversizing for summer (non-valorisable surplus production).

Variability over extended periods: in case of prolonged cloud cover (15 days for example), thermal storage can no longer ensure continuity - it’s sized to handle hourly or daily variations, not weekly ones. Guaranteeing 100% would require disproportionate storage (costs + land footprint).

Complementarity with existing assets: keeping your current thermal source as backup allows you to target the substitution rate at the lowest marginal cost - typically 10 to 90% depending on the processes. The last percentages would cost several times the average price.

The ALTO preliminary study identifies the optimal substitution rate for your site.

DNI (Direct Normal Irradiance) measures the direct solar energy received per m² on a surface perpendicular to the sun, expressed in kWh/m²/year.

To be distinguished from:
GHI (Global Horizontal Irradiance): total received on a horizontal surface, direct + diffuse light - useful for photovoltaics.
DHI (Diffuse Horizontal Irradiance): diffuse share (clouds, atmosphere).

For concentrating solar, only DNI matters: mirrors cannot concentrate diffuse light.

Orders of magnitude:
Northern France: 1,000-1,200 kWh/m²/year → not profitable
Southern France: 1,700-2,000 kWh/m²/year → profitable
Southern Spain: 2,000-2,400 kWh/m²/year → very profitable
Source: Global Solar Atlas · World Bank / Solargis / ESMAP, 2022

The profitability threshold for ALTO plants is typically around 1,200 kWh/m²/year.

Below this threshold, the plant can technically operate but only ~8 months/year: in high season (April-October) production is good, but over the 4 winter months DNI is too low and the plant is shut down. The average price per MWh then mechanically rises (fixed cost / low annual production) and profitability drops.

Above 1,200 kWh/m²/year, the plant produces all year round with acceptable seasonal variations, which allows the investment to be amortised on a stable base.

The DNI of your site can be consulted free of charge on the Global Solar Atlas (World Bank / ESMAP / Solargis) - global mapping based on more than 20 years of satellite data (EUMETSAT, NOAA) and atmospheric reanalyses (ECMWF, NASA), with a resolution of ~250m.

Global DNI map (Direct Normal Irradiance) - Global Solar Atlas / World Bank / Solargis

Click to explore the interactive map →

Source: Global Solar Atlas © The World Bank, Solargis, ESMAP - CC BY 4.0 license.

How to read the map: red / orange zones (≥ 1,800 kWh/m²/year) are particularly attractive; the profitability threshold is around 1,200 kWh/m²/year, covering the whole of Southern Europe. For a precise value at your site, click on the interactive map, select the DNI layer, and zoom in to your address.

Two notions often confused but essential for sizing a project.

Power (MW): instantaneous heat flow - what your process consumes at each moment. A 5 MW boiler produces 5 MW continuously at full load.

Energy (MWh or GWh): quantity consumed over a period - power × duration. This 5 MW boiler running 4,000 h/year consumes 20 GWh/year.

For an ALTO project:
Power sizes the solar field and storage (physical size of the installation)
Energy sizes the economic and carbon impact (bills and avoided tCO₂)
The ratio energy ÷ (power × 8,760 h) = load factor (typically 40-90% depending on the process)

Contracting

It all starts with a preliminary study, free of charge and with no commitment: our teams analyse your site, your thermal needs and the local solar potential. If conditions are favourable, we launch a detailed feasibility study - plant sizing, 20-year production simulation, financial structuring and drafting of the HPA contract.

All preparatory phases - detailed feasibility study, permitting and securing financing - generally represent 12 to 24 months. ALTO manages all administrative procedures (building permits, environmental authorisations) and puts in place the SPV financial structure - in full coordination with you.

Once everything is secured, construction begins: count on 9 to 12 months of works, run in parallel with your activity. Connection to your heat network is scheduled during a planned technical shutdown. After commissioning, ALTO operates and maintains the plant for the entire contract duration - 20 to 25 years. You receive heat, we handle the rest.

Starting point: contact us to start your personalised preliminary study - free and with no commitment.

See the full 5-step pipeline in the Heat-as-a-Service section.

The installation belongs to the plant’s financial partners, of which ALTO may be one (via the SPV), for the entire contract duration. This is precisely what spares you any upfront investment. At contract maturity, two options are provided: renewal under market conditions, or buyout of the installation at its residual value. This buy option is written into the contract from day one.

The installation requires a building permit. ALTO handles all administrative procedures: file preparation, submission to the local authority and follow-up of the review. If your site is classified ICPE (French environmental classification) or subject to local urban planning constraints, our teams carry out an upfront regulatory feasibility analysis.

Each project is held in a dedicated project company (SPV) separate from ALTO. In the event of an ALTO failure, the SPV - and therefore the installation - is not affected. As the equipment is standard and documented, asset ownership remains intact and operation can be taken over by any qualified operator. This architecture is a requirement of our financial partners.

End of contract (20-25 years): two options are provided from signature - renewal under market conditions, or buyout of the installation at its residual value. The buy option is written into the contract from day one.

End of plant life: ALTO technology is designed for full dismantling without soil artificialisation, thanks to its non-buried external foundations. Components follow a circular economy approach: reuse of foundation concrete via crushing, recycling of mirrors and steel structures, valorisation of end-of-life heat transfer fluids through dedicated channels.

Yes. The contract provides for early termination clauses with a pre-established and transparent buyout formula (residual asset value amortised over the remaining duration). The later the termination, the lower the amount. These conditions are negotiated upfront and locked contractually - there are no surprises. A corporate restructuring or site disposal doesn’t leave you trapped.

The contract includes a minimum annual production guarantee expressed in thermal kWh delivered at a given temperature. If ALTO fails to meet it - due to a breakdown, a maintenance default or system underperformance - contractual penalties apply. Unforeseen solar resource (exceptional weather) is covered upfront by careful analysis of the site’s historical irradiance data. You pay for heat delivered, not for the installation.

Financial guarantees are set up at signature: parent-company guarantee if you belong to a group, or bank GAPD covering the contract’s lifetime.

As the plant is built on foundations not anchored in the ground, ALTO retains the technical possibility of relocating it to another industrial site - this last resort helps preserve the asset’s value whatever the outcome.

This is one of the structural advantages of ALTO technology: the plant is built on non-buried external foundations, which makes it fully relocatable. In the event of a move or site disposal, the installation can be dismantled and reinstalled on your new industrial site, or transferred to another industrial client by ALTO. The contract sets out the terms of this transfer. You don’t lose the investment made, and ALTO doesn’t lose its asset.

Yes. ALTO takes out an all-risks construction insurance during installation, then an industrial operating insurance covering material damage, business interruption and civil liability for the entire contract duration. The technical and operational risk is entirely borne by ALTO - that’s the foundation of our model.

The contract is structured as an energy service contract, not as a finance lease. In most configurations, it allows for an off-balance-sheet treatment favourable to your borrowing capacity. We provide an accounting memorandum prepared with our financial partners to facilitate the analysis with your statutory auditor.

The heat price is set at signature and indexed on a public index (typically the industrial producer price index, or a composite index agreed between the parties). This indexation is transparent, predictable and contractually framed - it depends in no way on the gas or CO₂ price. This is precisely what industrial companies are looking for: a long-term visibility on their heat cost, protected from the ups and downs of energy markets.

Operation & maintenance

Construction duration is typically 9 to 12 months depending on installation size, once permits are obtained. Works run in parallel with your activity: connection to the existing heat network is scheduled during a planned technical shutdown (generally 1 to 3 days). Your industrial process is not interrupted during construction. A commissioning schedule is set jointly with your teams from the engineering phase. The plant then operates for a 25 to 30 year lifespan, with preventive maintenance carried out by ALTO over this entire period.

The HPA contract includes an annual availability commitment for the plant. In the event of underperformance attributable to ALTO - breakdown, maintenance default or undersizing - contractual penalties apply automatically. It’s ALTO that bears the operational risk, not the industrial company. Concentrating solar heat plants achieve in operation availability rates above 95% over sunlight hours. Preventive maintenance is scheduled during your technical shutdowns.

The ALTO plant runs in fully automatic mode: collectors track the sun’s path, heat transfer fluid pumps modulate production in real time according to process demand, and the system automatically switches between solar production and backup depending on conditions.

Remote supervision: ALTO continuously accesses the system via a secure connection. Any anomaly (temperature variation, performance drop, technical alarm) is detected and handled remotely whenever possible.

On-site intervention: in case of need for physical intervention, an ALTO technician comes within a contractual response time of 2 to 12 hours depending on criticality. An enhanced on-call service can be put in place to match your operational requirements.

No specific technical skill is mobilised in-house: you receive heat, we handle operations.

ALTO handles all maintenance - preventive and corrective - for the entire contract duration, with no technical skill to mobilise in-house. Preventive maintenance is scheduled jointly with your teams during your planned technical shutdowns; corrective maintenance is handled by our technicians with a contractually defined response-time commitment. A dedicated point of contact is assigned to each plant for the entire contract duration.

Yes. Each ALTO plant is equipped with a permanent remote monitoring system. As a client, you have access to a reporting portal displaying in real time thermal production, plant availability and cumulative CO₂ savings, in addition to monthly and annual reports automatically delivered.

The continuity of your industrial process is a non-negotiable requirement. The ALTO system is designed with a parallel connection to your existing heat source (gas boiler, steam network) which remains operational as backup. In the event of a breakdown or planned maintenance, the switchover to backup is automatic and seamless - your process doesn’t stop. Maintenance interventions are scheduled during your technical shutdowns, in coordination with your teams.

Note: for short interruptions and cloud passes, thermal storage takes over before the backup even kicks in - the process receives stored solar heat.

Maintaining mirror optical quality requires periodic cleaning to remove dust and atmospheric deposits. CSH plants typically consume 0.7 L of water per m² of collector and per cleaning, with a frequency of 2 to 8 cleanings per year depending on the local environment (dust, pollution, coastal proximity).

For a 1.5 MW ALTO plant (2,500 m² of collectors), that represents an annual consumption of about 4 to 14 m³ of water.

Note: unlike electrical CSP plants, ALTO plants do not consume water for cooling (no thermodynamic cycle) - their water footprint is therefore limited to cleaning only.

Our technology development roadmap includes automatic cleaning systems aimed at significantly reducing, or even eliminating, water use.

The plant consumes electricity to power three main functions: solar tracking motors (collector tracking throughout the day), circulation pumps for the heat transfer fluid, and monitoring and control systems.

This consumption typically represents 0.5 to 3% of the thermal energy produced - i.e. for a 1.5 MW plant producing 2-3 GWh thermal per year, around 10 to 90 MWh electrical per year.

Power is supplied via the local electricity grid. For full independence, this consumption can be covered by a complementary photovoltaic installation on site.

ALTO technology is sized to withstand the most severe conditions encountered in industrial operation.

Wind in production: collectors withstand up to 135 km/h - i.e. 3× the resistance of conventional troughs (45 km/h). Beyond this threshold, the system automatically switches to safety position (collectors flipped, concrete back facing the sky).

Wind in safety position: in this minimal aerodynamic configuration, the structure withstands well beyond any known weather event - mirrors and absorber tube perfectly protected.

Hail: in safety position, it’s the concrete back of the collectors that’s exposed to the sky - mirrors and absorber tube are perfectly protected. The robustness of the concrete handles the most severe hail episodes without damage.

Lightning: the installation is equipped with standard lightning protection, in accordance with the standards applicable to outdoor industrial infrastructure.

Monitoring systems automatically trigger protection procedures in case of alert.

Glossary
All powers (kW, MW) and energies (MWh, GWh) mentioned on this site refer to thermal heat, unless clearly stated otherwise.

HPA: Heat Purchase Agreement - long-term heat purchase contract (thermal equivalent of the PPA) · PPA: Power Purchase Agreement - long-term renewable electricity purchase contract (model analogous to HPA) · EPC: Engineering, Procurement & Construction - contractor in charge of design, procurement and construction · SPV: Special Purpose Vehicle - dedicated legal entity for each plant · CAPEX: Capital Expenditure - upfront investment costs (structure, mirrors, installation) · OPEX: Operating Expenditure - ongoing operations and maintenance costs · CSH: Concentrating Solar Heat (distinct from CSP which produces electricity) · DNI: Direct Normal Irradiance - direct solar radiation, key sizing parameter · TMY: Typical Meteorological Year - typical year built from 15-20 years of measurements, basis for sizing · TTF: Title Transfer Facility - reference natural gas index in Europe (Dutch hub) · ETS: Emissions Trading System - European emissions allowance trading scheme (EU ETS) · EUA: European Union Allowance - individual carbon allowance tradable in the EU ETS · CEE: French Energy Saving Certificates - French scheme requiring energy suppliers to finance energy efficiency actions · GAPD: French autonomous on-demand guarantee - irrevocable bank guarantee

Calibration sources

The simulator combines values fetched live (updated on each use) and values calibrated annually, drawn from eight public sources.

For the wholesale gas price, the simulator fetches live the 12-month rolling average of the TTF (Title Transfer Facility, Dutch hub quoted on ICE Endex). For the carbon market, the 12-month rolling EUA price is fetched from primary sales on EEX (European Energy Exchange).

For the transport and commercial margin components of the industrial pre-tax price, the simulator relies on the Eurostat nrg_pc_203_c dataset (Gas prices components for non-household consumers, published twice yearly by DG ENER) and the annual Market Monitoring Report from ACER (Agency for the Cooperation of Energy Regulators). For France, the CRE quarterly retail market observatory (Commission de régulation de l’énergie, French energy regulator) serves as a complementary reference.

For taxes, the simulator uses for France the official TICGN from the French Customs Code (article L312-37 of the CIBS), with an option to switch to the reduced large-consumer rate (article 265 nonies). The emission factor used for the ETS surcharge (0.201 tCO₂/MWh LHV, combustion only) is taken from the French ADEME Base Carbone v23, French reference consistent with the IPCC 2006 guidelines.

See how these sources are combined in the question Why does the gas price in the simulator differ from the TTF ?

Industrial solar heat

Break free from fossil fuels · Stabilize your price for 20 years
No longer subject to the markets

Heat-as-a-Service
Heat Purchase Agreement

Industrial applications

Modular · No technical expertise required
Tailored to every industrial process

Our technology

Its integration into the process

Heat accounts for nearly 50%
of global energy consumption

Projects in development

Legend

The team

Frequently asked questions

Get in touch

Industrial solar heat

Break free from fossil fuels · Stabilize your price for 20 yearsNo longer subject to the markets

Heat-as-a-ServiceHeat Purchase Agreement

Industrial applications

Modular · No technical expertise requiredTailored to every industrial process

Our technology

Its integration into the process

Heat accounts for nearly 50%of global energy consumption

Projects in development

Legend

The team

Frequently asked questions

Get in touch

Break free from fossil fuels · Stabilize your price for 20 years
No longer subject to the markets

Heat-as-a-Service
Heat Purchase Agreement

Modular · No technical expertise required
Tailored to every industrial process

Heat accounts for nearly 50%
of global energy consumption