Tewer Turned an EIC Accelerator Grant Into Heliostat Mirrors

A solar tower plant is only as good as its mirrors. Thousands of heliostats, sun-tracking frames covered in curved glass facets, have to bounce sunlight onto a receiver at the top of a tower, and every fraction of a degree of distortion spills energy. Tewer Engineering, a small engineering company on an industrial estate south of Madrid, says it has a better facet: a sandwich of two glass mirrors around a foam core, which it calls RST. In the 5 June 2019 cut-off the European Commission selected the company, listed simply as "TEWER", under the EIC SME Instrument Phase 2, the Horizon 2020 pilot of what is now the EIC Accelerator. The list names no other company for the project. The grant for AUTO-RST, "Flexible automated manufacturing of RST Facets", was €1,577,233 towards a total cost of €2,253,190, as a grant only.

The aim, in the words of the CORDIS summary, was to move "from the artisanal making of one-off individual facets to a pre-series production" line. By the project's own account that worked: in a CORDIS results article chief executive Marco Antonio Carrascosa Pérez says Tewer produced reflectors of 7.2 m², "the largest in the world", in about 20 minutes each. What the record does not show is the market that was supposed to follow. The project's final report set a sales goal of at least 700,000 m² for 2022 and 2023 and names one firm order: 650 facets for the Gemasolar plant in Spain.

Where Tewer Stands Now

Tewer Engineering is an active company. The Madrid commercial register lists it as active, with accounts deposited up to the 2024 financial year, according to empresia, and Infoempresa also shows it as "Activa". The two directories disagree on the filings: Infoempresa says the last ordinary accounts deposited are from 2014, empresia lists deposits for 2020 to 2024. Neither publishes the figures for free. Empresia puts annual revenue between €1 million and €2.5 million; Infoempresa says under €2 million, with 1 to 9 employees. A company profile on The Web Radar gives 11 to 50 staff and a founding year of 2013, while the register and CORDIS give 2014.

The register shows a company that has changed little in structure. It was set up in March 2014 as Thermal Power Engineering SL with €20,000 of capital, raised to €122,000 in November 2014, renamed Tewer Engineering SL and moved to Valdemoro in October 2021, and cut its capital by 30% to €85,400 in April 2023, according to the BORME acts collected by empresia and DatosCif. Ricardo Lozano Peña, the founding sole shareholder and director, handed the directorship to Carrascosa in January 2022. No equity round has been announced, and Tewer does not appear among the roughly 315 companies on the EIC Fund's list of invested companies; as a 2019 SME Instrument award, AUTO-RST came with no equity option.

The most recent public activity is research. In October 2025 Tewer reported the first year of SOLCARE, a €360,329.83 project for a solar collector that delivers heat to factories, with a €208,813.94 grant from the Community of Madrid and the European Regional Development Fund. The reference design it chose is a parabolic trough "with sandwich-type facets", a sign that the RST idea is being carried into a new product rather than dropped.

The Technology: Glass, Foam and Glass

Most heliostat facets are a silvered glass mirror glued to a steel backing. Carrascosa told CORDIS that glass and steel expand at different rates, so heat changes the curvature of the mirror and with it the focus; light reflected from neighbouring mirrors onto the steel backs can even "melt the glue". RST puts glass on both sides: a thin silvered front mirror and an aluminium back mirror, bonded to a polyurethane foam core that Tewer calls Solar Foam. Because both skins are glass, they expand together, and the back mirror reflects stray sunlight instead of absorbing it. The thin front glass, Carrascosa says, raises reflectivity to 95.5%. The company's product page sells the current version as the Tewer-RST3 facet, alongside an HTW135 heliostat, a WD3 parabolic trough collector and dish concentrators.

The sales case rests on scale and precision. Most commercial curved heliostat facets are 4 m² with an optical error of 1.2 to 1.4 milliradians, according to the CORDIS article; larger and more accurate facets mean fewer parts per hectare and more energy on the receiver. The 2019 proposal claimed this would cut the investment in a tower plant's solar field by 15%, "around 23M€ out of 156M€". CORDIS calls the facet "patented"; a web search for this article did not surface the patent publication, so its scope could not be checked.

What AUTO-RST Promised, and What CORDIS Shows

The grant agreement was signed on 30 September 2019 and the project ran from 1 October 2019 to 30 September 2022, according to CORDIS. The objective on the same page describes a project of "24 months", while the recorded dates span 36 months and three reporting periods; whether the project was extended is not stated. The final report and the results article, both written by the company, claim the technical targets were met or beaten. The commercial targets in the same report were not.

1. Pilot pre-series production lineDeliveredThe final report shows the erected pilot line and an RST facet mounted on a heliostat.
2. Facets of up to 7 m²Delivered7.2 m² reported in the CORDIS results article; no independent measurement is public.
3. Optical quality below 0.6 mradDelivered0.4 to 0.6 mrad, the company's own figure.
4. Cycle time of about 15 minutes per facetPartly"Close to 20 min per reflector", down from 2 hours.
5. At least 700,000 m² sold in 2022 and 2023Not achievedOne order of 650 facets from Q-Energy for Gemasolar; Abengoa's 7,500 m² for Khi Solar One was "interest". No later sale announced.
6. At least 5 clients by 2022Not achievedThe report names one buyer; an industrial heat case with ABInBev in Tenerife "did not result in a fruitful case".
7. On the market from Q1 2023UnverifiedThe Tewer-RST3 facet is on the product page; no launch or customer has been announced.

The final report is candid about the market. China's CSP players, it says, "are not actively engaging with foreign companies anymore"; in the Middle East it points to "a very interesting opportunity" at the Ashalim plant in Israel, and it sees a new opening in solar heat for factories after the energy crisis, which it says can be supplied "well below 40 €/MWh". None of these openings has since been reported as a contract. Whether the 650 Gemasolar facets were delivered, and whether the 30,000 m² replacement discussed for the same plant was ordered, could not be verified.

What Tewer Has Done Since the Award

Alongside the facet, Tewer kept selling engineering and assembly work to the big CSP builders. In a September 2021 post the company says Torresol Energy hired it as main contractor to assemble new heliostats at Gemasolar between September 2020 and March 2021, after earlier work on the assembly lines at Crescent Dunes and, with Batz Energy, at Noor III in Morocco. In March 2021 it announced the ATH146, a 146 m² heliostat developed with ACCIONA; Energías Renovables reported in September 2021 that it was under test at CIEMAT's Plataforma Solar de Almería. Its facets use a simpler design of mirror on three profiles, not the RST sandwich. The same year Tewer said it delivered eight transportable towers for an MSSR radar system, a step outside solar.

Much of its public activity since has been in research consortia. ACCIONA lists "Thermal Power Engineering S.L. (TEWER)" as a partner in Si-CO, a parabolic trough project of more than €3.2 million under the European CSP ERA-NET, and Tewer Engineering as a partner in LEIA, a €2.6 million project on smarter control of tower plants that ran to the end of 2025. Tewer itself reports a €584,092 share of the CDTI-funded NEOSOLAR project, for which it is designing a large parabolic trough reflector, and a part in PhoToHy, a €2,496,213 hydrogen project led by INAEL that CDTI supported with €1,677,793. On CORDIS the company's only other entry as a beneficiary is HELITE, a €50,000 SME Instrument Phase 1 feasibility study on heliostat fields in 2016.

The biggest bet is hydrogen. In 2023 Inspenet and New Mobility reported that Tewer and the catalyst maker Nanogap had formed HySun, a joint venture making hydrogen from water and concentrated sunlight, with Carrascosa as general director of both HySun and Tewer. Tewer says it now leads SOLAR-H2R, a 36-month, €3,183,238.50 project with Nanogap and Power2Hydrogen (HySun), funded with €2,546,590.80 from NextGenerationEU. In 2025 it reported tests at Almería of ThiCAV, a 3D-printed solar air receiver built with the Swedish firm Procada and University West, which it says heated air to 450 °C.

Why Europe Should Care

Concentrated solar power is one of the few renewable technologies that can store energy as heat and deliver it at night or as high-temperature steam, and Tewer's whole business is built on it. The Commission's EU Solar Energy Strategy of May 2022, part of REPowerEU, covers concentrated solar alongside photovoltaics and solar heat. The 2019 proposal put the solar field of its reference tower plant at €156 million, so a European supplier of cheaper, more accurate facets would matter for new plants and for the repair of existing ones, as the Gemasolar order shows. Tewer's own final report points to the same shift in demand: from big power plants to solar heat for industry, where gas boilers are the competition.

The Verdict

Tewer Engineering has not been asked for comment for this article. It is based entirely on public records, company statements and EU project data, linked throughout.