Beyond Renewable Energy: Giant Thermoses & Wastewater On Tap

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Now that low cost renewable energy is here, policy makers are scouting about for the most effective ways to stretch those clean kilowatts. The hunt is especially urgent in Germany and elsewhere in Europe, where emergency energy planning is under way if Russia turns off the spigot on its gas pipelines. With that in mind, let’s check out the goings-on in Berlin.

1. The Giant Renewable Energy Thermos

CleanTechnica has spilled plenty of ink on giant water batteries, but for the most part that involves cold-water energy storage systems, aka pumped storage hydropower. Technically speaking, pumped storage systems are energy-agnostic on the uphill side with gravity doing the work downhill, but they have been gaining traction as bulk systems for storing renewable energy.

Concentrating solar power systems also come to mind as renewable energy storage systems. However, the Berlin renewable energy storage system is not that.

Associated Press has the scoop on this Berlin’s new energy storage system, which was dreamed up by the Swedish firm Vattenfall. The heart of the system is a giant tank almost 150 feet high, which can hold 56 million gallons of hot water.

“The new facility unveiled Thursday at Vattenfall’s Reuter power station will hold water brought to almost boiling temperature using electricity from solar and wind power plants across Germany,” Jordans reports. “During periods when renewable energy exceeds demand the facility effectively acts as a giant battery, though instead of storing electricity it stores heat.”

2. Sucking Up Excess Heat From Wastewater

CleanTechnica has also been eyeballing energy innovation in the municipal wastewater area, mainly in the wastewater-to-biogas area (biogas from manure is a whole ‘nother kettle of fish). Berlin is cooking up something different. Their wastewater-to-energy system is similar to one launched in Philadelphia about 10 years ago, in which heat from the sewer system is captured via heat pumps.

A City of Philadelphia blog post from 2012 describes the energy-scavenging system, which takes advantage of the fact that municipal wastewater is warmed by the use of hot water appliances as well as microbial activity, resulting in an average temperature of 60 degrees Fahrenheit in winter and 75 degrees or more in the summer.

The Berlin project is somewhat more modest in scale, but it could lead to bigger things. Last summer the energy firm E.ON described a 50,000 square meter office building supplied with both heat and AC through a heat exchange system that runs through the sewer by the building.

The system provides for about half of the building’s heating and cooling needs, and there’s plenty more where that comes from. E.ON estimates that Germany could supply 14% of its heating and cooling needs in buildings with renewable energy from wastewater heat exchange.

As for who’s gonna pay for all this, E.ON also states that “the energy supply solution with the wastewater heat exchanger is as cheap as a conventional solution with fossil-generated district heating.”

“A decentralized, space-saving energy supply from wastewater enables sustainable heat and cold in the middle of the city, where space for wind and solar energy is usually limited,” they add.

3. A Geothermal Well In Every Pot

The E.ON heat exchange system is a form of geothermal energy, except that it leverages the built infrastructure instead of having to drill new geothermal wells.

The built environment angle is a good fit for Berlin, which has strict regulations regarding geothermal wells because almost its entire supply of drinking water supply comes from groundwater sources within the city limits.

Nevertheless, as a renewable energy resource the geothermal prize is a tantalizing one. The number of geothermal wells in Berlin shot up from just 132 in 2004, to about 3,500 midway through 2018.

“This trend is continuing, and is an important factor in the energy mix for the future use of renewable energy sources,” the Berlin Environmental Atlas notes. “Unlike most other renewable energy sources, such as wind, hydropower or solar power, geothermal energy is an energy form which is independent of the weather, of the time of day and of the season of the year; it is virtually always available.”

Sure enough, scale-up is in the works. Last December the GFZ German Research Centre for Geosciences provided an update on its exploratory drilling for the new GeoFern (Geothermal District Heating Supply Berlin) project, which aims to “create the conditions for a climate-friendly district heating supply for Berlin with the help of a seasonal geothermal aquifer heat storage system.”

“Porous, deep aquifers have great potential for seasonal heat storage,” they explain. “During the summer months, they can absorb surplus heat from the production of combined heat and power plants or industrial plants, for example, which is pumped down there in the form of hot water.”

4. A Solar Powered Mail-Boat

On the small-scale side of renewable energy, Berlin planners also expect solar panels to play a significant part in the urban energy transition. Back in 2020, the city developed a master plan calling for mandatory rooftop solar panels for new and existing buildings with rollout beginning in January 2023, and the enabling legislation was passed last month.

The city’s waterways may also come into play. Last year Deutsche Post (a DHL branch) proposed to send packages across the Spree on a solar-powered ship.

“The project is part of a joint research project in which the Technische Universität Berlin (TU) is also involved,” the city explained.

The solar boat project is aimed at shifting traffic off city roads. While its impact in terms of additional renewable energy is negligible, a fleet of solar powered delivery boats could help relieve congestion on urban roads. If all goes well the boat could start ferrying packages as early as this summer.

5. The Hydrogen Connection

Of course, no mention of renewable energy in Berlin would be complete without a mention of green hydrogen. Vattenfall has a hand in that area as well, along with other partners in the H2 Berlin initiative.

“Berlin has the potential to become a pioneer in the sustainable use of hydrogen,” they explain. “For example, household waste could be used to produce green hydrogen. Hydrogen can also transport energy and offers a possible solution to the storage problem of renewable energy.”

When the topic turns to green hydrogen, water electrolysis is typically the technology of choice. However, that process requires significant renewable energy input, and it appears that H2 Berlin aims to produce green hydrogen without relying too heavily on wind or solar power.

Instead, the focus — for now, at least — appears to be capturing biogas from wastewater, as a feedstock for hydrogen. Last spring, H2 Berlin launched a demonstration facility at a wastewater treatment plant in the city, with an assist from the firm Graforce, which is lending its plasma electrolysis technology to the effort.

“Whereas water electrolysis needs 50kWh/kg H2, the production of 1kg hydrogen from methane takes only 10kWh or 20kWh from wastewater, Graforce explains.

The methane connection is the key. The main source of hydrogen today is methane from natural gas, and the race is on to find an economical alternative.

In terms of renewable energy and hydrogen sourcing, H2 Berlin is treading somewhat cautiously on the use of “green hydrogen” to describe its wastewater-to-hydrogen solution. They prefer “light green,” perhaps because in reference to the use of recycled waste as a feedstock.

Either way, hydrogen is here to stay. Much has been made of a certain new gigafactory in Berlin for the manufacture of battery-electric cars, but Siemens’s forthcoming electrolyzer factory in the city — located at a former gas turbine plant — will most likely have a more significant impact on the pace of global decarbonization.

For the record, Siemens plans for the factory to run on 100% renewable energy.

Follow me on Twitter @TinaMCasey.

Photo: Plasma electrolyzer for wastewater-to-hydrogen facility, located at a wastewater treatment plant in Berlin, Germany (courtesy of Graforce).

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Tina Casey

Tina specializes in advanced energy technology, military sustainability, emerging materials, biofuels, ESG and related policy and political matters. Views expressed are her own. Follow her on LinkedIn, Threads, or Bluesky.

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