Giant thermos and sewage on tap
Now that low-cost renewable energy is here, policymakers are looking for the most efficient ways to stretch those clean kilowatts. The hunt is particularly urgent in Germany and elsewhere in Europe, where contingency energy planning is underway if Russia shuts off the tap on its gas pipelines. With that in mind, let’s look at what’s happening in Berlin.
1. The giant thermos of renewable energies
Clean Technica Much has been written about giant water batteries, but for the most part it involves cold water energy storage systems, i.e. pumped storage hydroelectricity. Technically speaking, pumped storage systems are energy independent upstream, with gravity doing the work downstream, but they have gained popularity as bulk systems for storing renewable energy.
Concentrated solar power systems also come to mind as renewable energy storage systems. However, Berlin’s renewable energy storage system is not that.
Associated Press has the scoop on this new energy storage system in Berlin, designed by the Swedish firm Vattenfall. The heart of the system is a giant tank nearly 150 feet tall, which can hold 56 million gallons of hot water.
“The new installation unveiled at Vattenfall’s Reuter power station on Thursday will hold water brought to near-boiling temperature using electricity from solar and wind power plants across Germany,” Jordans reports. “During times when renewables exceed demand, the facility effectively acts as a giant battery, although instead of storing electricity, it stores heat.”
2. Suck excess heat from waste water
Clean Technica has also been attentive to energy innovation in the field of municipal wastewater, mainly in the field of converting wastewater into biogas (biogas from manure is another story). Berlin is preparing something different. Their wastewater-to-energy system is similar to one started in Philadelphia about 10 years ago, in which heat from the sewer system is captured through heat pumps.
A 2012 City of Philadelphia blog post describes energy recovery systemwhich 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 the winter and 75 degrees or more in the summer .
The Berlin project is a bit more modest, but it could lead to bigger things. Last summer, the energy company E.ON described a 50,000 square meter office building supplied with both heating and cooling by a heat exchange system which goes to the sewer near the building.
The system covers about half of the building’s heating and cooling needs, and there’s a lot 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 waste water heat exchange.
As to who is going to pay for all this, E.ON also states that “the energy supply solution with the waste water heat exchanger is as cheap as a conventional solution with fossil fuel district heating”.
“A decentralized and 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 each pot
The E.ON heat exchange system is a form of geothermal energy, except that it harnesses built infrastructure instead of having to drill new geothermal wells.
The built environment angle suits Berlin well, which has strict regulations regarding geothermal wells, as nearly all of its drinking water supply comes from underground water sources within the city limits.
Nevertheless, as a renewable energy resource, the geothermal price is enticing. The number of geothermal wells in Berlin rose from just 132 in 2004 to around 3,500 in mid-2018.
“This trend continues and is an important factor in the energy mix for the future use of renewable energy sources,” notes the Berlin Environmental Atlas. “Unlike most other renewable energy sources, such as wind, hydroelectricity or solar energy, geothermal energy is a form of energy that is independent of time, day and season of the year; it is almost always available.
Indeed, the scaling is in progress. Last December, Germany’s GFZ research center for geosciences reported 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 climate for Berlin with the help of a seasonal geothermal aquifer heat storage system.
“Porous and deep aquifers have great potential for seasonal heat storage,” they explain. “During the summer months, they can absorb excess heat from the production of cogeneration plants or industrial plants, for example, which is pumped into them as hot water.”
4. A solar-powered mail boat
On the small-scale renewable energy side, Berlin city planners also expect solar panels to play an important role in the urban energy transition. In 2020, the city drafted a master plan calling for mandatory solar panels on the roofs of new and existing buildings with deployment starting in January 2023, and enabling legislation was passed last month.
“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 aims to move traffic off the city’s 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 transporting packages this summer.
5. The hydrogen connection
“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 renewable energy storage problem.
When the topic turns to green hydrogen, water electrolysis is usually the technology of choice. However, this process requires a large input of renewable energy, and it seems that H2 Berlin aims to produce green hydrogen without relying too much on wind or solar power.
Instead, the focus – for now, at least – seems to be on capturing biogas from wastewater, as a feedstock for hydrogen. Last spring, H2 Berlin launched a demonstration installation at a wastewater treatment plant in the city, with the help of the company Graforcewhich lends its plasma electrolysis technology to the effort.
“While water electrolysis requires 50 kWh/kg H2, producing 1 kg of hydrogen from methane only takes 10 kWh or 20 kWh from wastewater,” says Graforce.
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 supply, H2 Berlin somewhat cautiously uses the use of “green hydrogen” to describe its solution for turning wastewater into hydrogen. They prefer ‘light green’, perhaps because it refers to the use of recycled waste as a raw material.
Either way, hydrogen is here to stay. Much has been said about a certain new gigafactory in Berlin for the manufacture of battery electric cars, but Siemens’ next electrolyser plant in the city – located in a former gas turbine plant – will most likely have a greater impact on the pace of global decarbonization.
For the record, Siemens expects the plant to run on 100% renewable energy.
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Photo: Plasma electrolyser for the wastewater-to-hydrogen plant, located in a sewage treatment plant in Berlin, Germany (courtesy of Graforce).
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