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 emergency energy planning is underway if Russia turns off the tap on its gas pipelines. With that in mind, let’s take a look at what’s going on in Berlin.
1. A giant renewable energy thermos
CleanTechnica has spilled a lot of ink on giant water batteries, but much of it concerns cold water energy storage systems, or pumped hydropower. Technically speaking, pumped storage systems are energy agnostic on the hillside, with gravity doing the work downhill, but they are gaining traction as large-scale renewable energy storage systems.
Concentrated solar systems also come to mind as renewable energy storage systems. However, Berlin’s renewable energy storage system is not.
Associated Press has an overview of this new Berlin-based energy storage system devised by Swedish firm Vattenfall. At the heart of the system is a giant tank nearly 150 feet tall that holds 56 million gallons of hot water.
“The new facility unveiled on Thursday at Vattenfall’s Reuter plant will hold water brought to near-boiling temperature using electricity from solar and wind farms across Germany,” Jordans reports. “During periods when renewable energy exceeds demand, the device effectively acts as a giant battery, although it stores heat instead of storing electricity.”
2. Extraction of excess heat from waste water
CleanTechnica it also pursues energy innovation in municipal wastewater, particularly wastewater to biogas (manure biogas is a whole ‘nother kettle of fish’). Berlin is preparing something else. Their wastewater-to-energy system is similar to one started in Philadelphia about 10 years ago, in which heat from the sewage system is captured using heat pumps.
A 2012 City of Philadelphia blog post describes an energy purification system that takes advantage of the fact that municipal wastewater is heated by 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 somewhat more modest in scope, but could lead to bigger things. Last summer, energy firm E.ON described a 50,000 square meter office building supplied with both heat and air conditioning through a heat exchange system that runs through the building’s sewers.
The system provides 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 meet 14% of its heating and cooling needs in buildings with renewable energy from waste water heat exchange.
As for who will pay for it all, E.ON also states that “a waste heat exchanger energy supply solution is as cheap as a conventional fossil fuel district heating solution”.
“Decentralized, space-saving energy supply from wastewater enables sustainable heat and cooling in the middle of the city, where space for wind and solar energy is usually limited,” they add.
3. Geothermal well in each pot
E.ON’s heat exchange system is a form of geothermal energy, except that it uses built infrastructure instead of having to drill new geothermal wells.
The built environment angle is well-suited for Berlin, which has strict regulations on geothermal wells, as almost all of its drinking water supply comes from underground sources within the city limits.
However, as a renewable energy source, geothermal has an exciting price tag. The number of geothermal wells in Berlin has grown 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,” reports the Berlin Environmental Atlas. “Unlike most other renewable energy sources such as wind, hydro or solar energy, geothermal energy is a form of energy that is independent of weather, time of day and season; is practically always available.”
Sure, the enlargement is in the works. Last December, the GFZ German Research Center 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 using a seasonal geothermal aquifer heat storage system .
“Porous, deep collectors have great potential for seasonal heat accumulation,” they explain. “In the summer months, they can absorb, for example, excess heat from the production of cogeneration units or industrial plants, which is pumped there in the form of hot water.”
4. Solar powered mail boat
On the small-scale renewable energy side, Berlin’s planners also expect solar panels to play a significant role in the city’s energy transition. In 2020, the city developed a master plan calling for mandatory rooftop solar panels for new and existing buildings, starting in January 2023, and enabling legislation was approved last month.
Urban waterways can also come into play. Last year, Deutsche Post (a branch of DHL) proposed sending parcels 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 moving traffic from city roads. While its impact in terms of additional renewable energy is negligible, a fleet of solar-powered delivery barges could help ease congestion on city roads. If all goes well, the ship could start carrying packages as early as this summer.
5. Hydrogen bonding
Of course, no mention of renewable energy in Berlin would be complete without a mention of green hydrogen. Vattenfall also has a hand in this area together 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 problem of storing renewable energy.”
When the topic turns to green hydrogen, water electrolysis is usually the technology of choice. However, the process requires a significant input of renewable energy, and H2 Berlin seems to be aiming to produce green hydrogen without relying too much on wind or solar power.
Instead, the focus – at least for now – seems to be on capturing biogas from wastewater as a feedstock for hydrogen. Last spring, H2 Berlin launched a demonstration facility at the city’s wastewater treatment plant with the help of Graforce, which is lending its plasma electrolysis technology to the effort.
“While electrolysis of water needs 50 kWh/kg H2, producing 1 kg of hydrogen from methane requires only 10 kWh or 20 kWh from waste water,” explains Graforce.
The methane connection is key. The main source of hydrogen today is methane from natural gas, and there is a race to find an economical alternative.
When it comes to renewable energy and hydrogen production, H2 Berlin treads somewhat cautiously when it comes to using “green hydrogen” to describe its wastewater-to-hydrogen solution. They prefer “light green”, perhaps because of the use of recycled waste as raw material.
Either way, hydrogen is here to stay. Much has been made of a certain new gigafactory in Berlin for the production of battery electric cars, but the upcoming Siemens electrolyser factory in the city – housed in a former gas turbine factory – is likely to have a more significant impact on the pace of global decarbonisation.
For the record, Siemens plans to have the factory run on 100% renewable energy.
Follow me on Twitter @TinaMCasey.
Photo: A plasma electrolyser for a wastewater-to-hydrogen plant, located at a wastewater treatment plant in Berlin, Germany (courtesy of Graforce).
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