Published on June 24th, 2014 | by Silvio Marcacci18
Sustainable District Heating From Seawater? It’s Happening In Holland
June 24th, 2014 by Silvio Marcacci
When the fishing industry in Duindorp, a small community near The Hague, Holland withered after years of prosperity, the local government saw an opportunity to rebuild local housing dating from the 1930’s into modern low-income homes.
Residents made it clear they wanted renewable district heating, but developers were challenged to provide renewable power at prices compliant with Dutch principles mandating consumer costs stay at the same level for clean energy. “We asked – well, where do we get sustainable energy from,” said Paul Stoelinga, senior consultant at Dutch environmental engineering firm Deerns International.
The answer was as apparent as it was improbable, according to Stoelinga. “The sea is nearby, and these people have a relationship with the sea because of former industry, so why don’t we retrieve heat from the sea?” (Full disclosure – while my trip was sponsored by the Dutch Government’s Ministry of Foreign Affairs, it had no involvement in the editorial process of this post).
It’s a tricky proposition, considering Northern European winters, but from this realization sprung the world’s first district heating system in 2008, turning seawater into a sustainable source of energy for 800 homes – one that’s now in use at several other sites across Europe.
The small nondescript white building housing the power plant sits just inside Duindorp’s harbor, but the innovative approach to sustainable heating stands out as a promising solution for waterfront communities in the clean energy transition.
Intake valves start the process by drawing seawater into the facility through a five-stage filtering process designed to prevent corrosion and protect sea life, ensuring fish can always escape the intake. That protective step is important, considering the system draws between 26,000-190,000 gallons per hour.
During summer months, harbor water hovers around 70 degrees Fahrenheit, and the facility sends filtered water through five miles of pipes to the homes, where in-home grid-connected 5kWh-capacity heat pumps boost temperatures to between 110-150 degrees Fahrenheit for heating and warm water through all-electric systems.
In winter months, when seawater temperatures dip as low as 37 degrees Fahrenheit, a 3-megawatt (MW) heat exchanger boosts water temperatures up to a level each home’s heat pump can handle – most heat pumps will fail when water falls below 50 degrees.
An Efficient, Economical, Environmental Solution
Combined with home insulation, this process creates a cost-effective heating source generating 15 kilowatt-hours (kWh) of heat from just 1kWh of electricity, according to a Deerns presentation, reducing the coefficient of performance for home heat pumps by just 5% while reducing emissions 50% compared to conventional heating using natural gas as a power source.
And, the system’s operations could technically represent zero emissions. Deerns originally proposed powering the plant with wind energy via two on-site 1.5MW turbines, but was turned down by the local government over noise and safety concerns. “It was a disappointment for us because we wanted the project to be 100% renewable,” said Stoelinga.
Solar energy was explored as an option, but photovoltaic panel costs would have put project costs above consumer price thresholds – a situation that could change as solar power costs continue to plummet.
While Duindorp’s seawater heating may be an environmentally friendly solution, it’s also worth noting the system’s relatively affordable economics. Total construction costs for the facility were just €7.5 million, and consumers pay a fixed price of €70 per month for sustainable heat – comparable to costs before the system was completed, all according to Stoelinga.