Full output from wind and sun works with our cooling
Renewable plants stand where maintenance is expensive: on towers, across open land, at sea. We design heat sinks for inverters, generators and storage systems that run there for decades, even under salt spray, dust and thermal cycling.
More than the power electronics gets hot in the plant.
Besides inverters we cool generators, busbars, storage systems and housings. At hard-to-reach sites, cooling decides how often someone has to climb up.
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Converters & inverters
IGBT and SiC modules under strongly fluctuating load.
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Generators & stators
Removing waste heat directly at the winding.
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Power rails & busbars
Absorbing waste heat in the power distribution.
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Battery storage
Cell temperature control for service life and safety.
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Transformers & chokes
Passive components with high continuous losses.
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Nacelle & control cabinet cooling
Air-to-water cooling instead of an air conditioner.
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Electrolysers
Power electronics and process cooling in hydrogen production.
Ruggedness · Low maintenance · Yield
Every service call on a nacelle or in a solar park costs more than the part. That is why we design for service life and low maintenance, and so that the plant does not have to curtail at full output.
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Ruggedness
Designed against salt spray, humidity, dust and thermal cycling, with suitable material and surface protection.
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Low maintenance
Flushable geometries and matched material pairings, so service intervals stay long.
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Yield
Sufficient cooling reserve so the plant does not have to curtail thermally at high feed-in.
What we supply for renewable generation
- Cold plates (liquid cooling plates) : for converters and inverters.
- Stator cooling : for generators.
- Busbar coolers : for busbars and distribution.
- Storage cooling : for battery systems.
Three designs that make the difference in renewables.
Multipress
Press-fitted tubes in the cold plate: a process-reliable, robust design for large areas and long parts. Available in copper, copper-nickel, stainless steel or aluminium.
Structureflow
Cooling channels integrated directly into the load-bearing structure. Fewer interfaces, less thermal resistance, and one part instead of an assembly.
Turbulators
Up to 40 % more cooling capacity at an acceptable pressure drop. We position them to the millimetre beneath your hotspots.
Everything from one source, from development to series production.
COOLTEC handles your thermal management completely: one contact, one process, from the first idea to series delivery. You join wherever you stand. Development, simulation and design are optional.
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Development & simulation
We develop, simulate and design your cooling solution. We test it virtually before we produce anything physically.
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Manufacturability & cost
You already know what you need? We assess manufacturability and optimise your design for series production.
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Samples & prototypes
Samples in around 6-8 weeks as standard, or 2-4 weeks by express, depending on product and complexity.
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Series production
From one supplier: highly automated high-tech manufacturing in Germany, low-cost series from Asia.
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Supply & lifecycle
Framework contracts, stockholding, last-time buy: we secure your supply across the entire product lifecycle.
Renewables Thermal Guide: cooling for wind, solar and storage
This is design knowledge rather than a product catalogue: what cooling solutions look like when they have to work for decades at hard-to-reach sites with little maintenance.
Sebastian Krüger
Bring your thermal challenge: heat load, installation space, medium, ambient conditions. In the first call Sebastian works out the right approaches with you and puts together the team we need for it, from application engineering, production engineering and thermal engineering. You will not be put on hold.
Frequently asked questions
Why do cold plates corrode in solar and wind inverters?
Corrosion damage to cold plates in inverters almost always has one of three causes, and none of them is plate quality: unsuitable or aged coolant without effective inhibitors, a mixed installation of different metals in the circuit, or moisture from outside on an inadequately protected surface. Open-field plants add external corrosion on top of that: a bare aluminium cooler near the coast or in an industrial atmosphere needs a suitable surface treatment, and thicker anodising is more effective here than a thin decorative layer. That is why we assess coolant, materials in the circuit and the external environment together on every enquiry. Limit: a surface treatment does not protect against an aggressive coolant on the inside. The inside cannot be re-coated, so the material choice decides there.
Read more –>Do the coolers withstand 20 years of outdoor operation?
A metal cooler with no wearing parts can reach service lives of two decades. Its life is not decided by the metal, though, but at three other places: care of the coolant, the seals and hoses, and the surface treatment against external corrosion. Elastomers age independently of operation and are usually the first parts that have to be replaced; a cooling concept with metal-sealing fittings instead of O-rings therefore lasts longer but is more demanding to assemble. For plants with long service lives we also plan spare-part availability and document geometry and materials so that a rebuild remains possible years later. Limit: we do not give a service-life commitment in years, because it depends entirely on operating and maintenance conditions we do not control.
Read more –>Air or liquid for an outdoor inverter?
For outdoor inverters, air cooling is the simpler solution as long as it is thermally sufficient: it needs no circuit, no antifreeze concept and no leak testing. But it has two weaknesses outdoors. An open air path draws dust, pollen and moisture into the unit, and cooling capacity falls as the ambient temperature rises, precisely when the plant is delivering its highest output. Liquid cooling decouples the unit from the ambient air, allows sealed enclosures with a high protection rating and moves heat rejection to a freely positioned cooler. The price for that is a circuit, pump, antifreeze and maintenance. Limit, honestly stated: at small power classes liquid cooling is oversized. If your heat load is manageable with air, we recommend air, even though we earn more on a cold plate.
Read more –>Can heat sinks be bonded to a housing instead of bolted?
Bonding is possible and is used where a bolted joint is not feasible by design, or where the adhesive joint also has to seal, for example with a heat sink mounted from outside onto a sealed enclosure. The thermal price is considerable: even a thermally conductive adhesive conducts heat many times worse than metal, so the adhesive layer becomes the governing resistance. So keep the adhesive layer as thin and as uniform as possible, and make sure the surface is flat. Silicone-based adhesives are permanently elastic and resistant to thermal cycling but conduct particularly poorly; filled epoxy adhesives conduct better but are stiff and transmit stresses. Limit: in a corrosive environment such as a coastal site, the adhesive joint decides the service life of the entire assembly. There we recommend a mechanical safeguard in addition to bonding.
Read more –>How long does a liquid cooler last, and what has to be maintained?
A metal liquid cooler has no wearing parts and is designed for the service life of the system. The limits are not aluminium or copper but corrosion from unsuitable or aged coolant and fatigue at the connections. In practice, maintenance therefore means: change the coolant at the prescribed interval, check inhibitor effectiveness, inspect the fittings. Clogging is an issue with internally structured plates with narrow channels if the circuit carries particles; here a filter in the system is the effective measure, not a larger channel cross-section. For projects with service lives spanning decades we plan spare-part availability and document materials and tube geometry so that a rebuild is possible later. Limit: we cannot give a service-life commitment in operating hours, because it depends entirely on coolant care and system conditions.
Read more –>How do you get from a need to a design when no specification exists yet?
If the specification is missing, three inputs are enough for a first sound proposal: heat load, available installation space and the temperature the component must not exceed. Everything else (coolant, volume flow, process) we can propose rather than ask for. What does not work is a design without a heat load: a cooler with an unknown thermal load cannot be designed, and anyone confirming thermal values anyway is working with assumptions. That is exactly what we have encountered in competitive situations where customers had received confirmed data without the heat load being known. We keep our distance from that. Limit: simulation results are calculated results. We label them as such and point out that they need to be confirmed by measurement on the real set-up.
Read more –>How do you design for thermal resistance?
We start from your load case: heat load, distribution across the area, permissible component temperature, inlet temperature, volume flow and installation space. This yields the Rth budget, which we test in thermal simulation against variants of the channel routing, before design work begins.
How do you design for strongly fluctuating load?
Via the load profile rather than the nominal point. With wind and solar, the temperature cycles are often more critical than the maximum temperature: they determine the service life of the bonding layers inside the power module.
Which materials do you process, and how do you choose correctly?
We work with copper, copper-nickel, stainless steel and aluminium. The choice follows three criteria: thermal conductivity, media compatibility and mechanical requirement. We frequently combine materials, with the conductive one at the heat source and the resistant one at the medium.
How do you ensure leak tightness?
Pressure testing of every part is our standard; for demanding applications we additionally test with a helium leak test and document the leak rate per part. We set the target leak rate before design.
In which sizes do you manufacture heat sinks and liquid cold plates?
From a 30 mm microchannel cooler to a 3 m (30,000 mm) cold plate, and up to a fully cooled large precision part. Size alone does not decide what is possible; material, design and tolerance do. Give us your dimensions and we will tell you in which design we can produce them.
Are your parts suitable for offshore and coastal sites?
We match material and surface protection to the ambient conditions; copper-nickel and stainless steel are often the right choice here.
Do you also cool generators and storage systems?
Yes. Stator cooling for generators and area temperature control for battery storage are part of our range, as are switchgear and container cooling.
Which quantities and lead times are possible?
Samples in around 6-8 weeks as standard, 2-4 weeks by express. For series production we manufacture in a highly automated plant in Germany; cost-sensitive standard parts come from our joint ventures in Asia.
Do you work under NDA?
Yes, that is the norm for us. We sign your non-disclosure agreement or provide ours. We never pass on customer projects or application details.
Cooling for renewable generation: what matters technically
Plants for wind, solar and storage stand where service is expensive. That shifts the design from performance to service life and corrosion resistance.
How we design a cooling solution
Every design starts from the same boundary conditions: heat load Pv, maximum permissible component temperature, ambient or inlet temperature and the available contact area. Only these determine which cooling strategy is feasible at all.
The four key parameters of a thermal system
Five steps to the right cooling solution
What influences the thermal resistance of an air-cooled heat sink
Materials: thermal conductivity and flow limits
The choice of material determines thermal performance and service life. If the flow velocity in the tube exceeds the maximum recommendation, the medium mechanically removes the protective passive layer, which leads to erosion and leakage.
| Material | Thermal conductivity at 20 °C | Max. flow velocity |
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| Copper / copper alloys | 305–394 W/m·K | 2,0 m/s |
| Aluminium / Al alloys | 125–210 W/m·K | 1.8 m/s (structures 1–2 m/s) |
| Copper-nickel (CuNi) | - | 3,5 m/s |
| Stainless steel | low conductivity, very good corrosion resistance | 4,5 m/s |
| Graphite (parallel to the layer plane) | up to 2000 W/m·K, technically 140–160 W/m·K | - |
| Sintered ceramics (BN, SiC) | 100–200 W/m·K, electrically insulating | - |
The data we need for your design
The more complete the boundary conditions, the faster we get from a first estimate to a reliable CFD simulation. This checklist comes from the Cool How Report and is the basis of every design discussion.
Load cycling as the limit on service life
Wind and solar inverters rarely work at the nominal point. The load follows the weather, and every cycle stresses the bonding layers inside the power module.
We therefore design for a small temperature swing across the load cycle, not only for the maximum junction temperature. That measurably extends module life.
Corrosion at exposed sites
Salt spray, humidity and dust attack heat sinks from outside, the material pairing from inside. Both have to match the site class.
Copper-nickel and stainless steel are often the right choice at coastal and offshore sites. We agree material, surface protection and medium together and document the release.
Low maintenance as an economic factor
A service call on a nacelle costs many times the price of the part. Every maintenance interval the design saves feeds directly into operating costs.
We design for flushability, without dead corners, and match media and inhibitors. That reduces deposits more than any downstream filter concept.
From prototype to series
The most expensive mistake is a prototype that works thermally but cannot go into series. That is why we assess manufacturability and cost in parallel with the thermal design, not afterwards.
Because development, manufacturing, testing and delivery are all in one hand at COOLTEC, nothing is lost at these transitions, from the first load case to the last-time buy.
Get the Renewables Thermal Guide
Three details, one click, instant download. After that you decide whether we talk about your project.
Is your plant derating thermally?
Send us your load profile: heat load, site conditions, installation space, medium. We will tell you whether and how we can solve it.