| Title | Heat of Molten Lava Used for Space Heating |
|---|---|
| Authors | Sveinbjorn BJORNSSON, Baldur JÓNASSON, Már KARLSSON |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | molten lava, heat extraction, space heating |
| Abstract | The Eldfell lava flow on Heimaey in 1973 became 130 m thick. The thickness of molten lava exceeded 100 m in many regions. Drilling showed that the intensely fractured crust was saturated with 100°C steam from surface down to the molten horizon, where the temperature escalated within a few metres up to the 1050°C of the melt. At the surface of the lava steam condensed in the tephra cover and blocked outflow of steam. The steam was therefore contained between the tephra and the molten horizon. Soon after the eruption ended interest developed to use the steam for space heating in the town of Heimaey with 4000 inhabitants. Theoretical calculations indicated that the 100 m thick molten section would not solidify through until 14 years after the end of the eruption. With controlled irrigation one might therefore be able to generate steam like on a hot pan, until the irrigation water had eaten its way through the melt and was lost through the lava bottom. Experiments also demonstrated that one could suck steam from the lava flow over long distances. This encouraged belief in using the lava heat and it was decided to construct a heating system for the whole of the town. The first phase of this system began operation near the end of year 1978, five years after the eruption ended, and it reached full capacity when the distribution system in town was completed in 1982. Selected areas with 100 m thickness of melt were subjected to controlled irrigation. The generated steam was collected into wells of wide concrete pipes and sucked to chambers of heat exchangers with the aid of chimneys. The only mechanical pumps required were those that distributed the irrigation water. The water circulating in the distribution system of the town came 35°C hot from the town to the heat exchangers where it was heated to 80°C. The cost of generating heat from the lava was about 20% to 30% of the cost of heat from oil. The generation of steam from the lava worked well until year 1988 but after that difficulties arose as the irrigation water found passages through fractures and escaped through the bottom of the flow instead of evaporating. |