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Il calore che si accumula nelle città e al di sotto di esse è nettamente superiore rispetto a quello misurabile in aperta campagna e ha un grande potenziale come fonte energetica. Lo rileva uno studio del politecnico federale di Zurigo, condotto da Peter Bayer e Jaime Rivera e pubblicato nel periodico "Renewable Energy".
Nei grandi centri abitati il calore superficiale viene veicolato nel sottosuolo tramite strade, cantine e fogne. Al riscaldamento del terreno contribuiscono inoltre anche altre fonti quali gallerie e reti di teleriscaldamento. Grazie a tale "effetto isola" il potenziale per il suo sfruttamento negli agglomerati è fino al 40% superiore rispetto all'ambiente circostante.
La capacità termica che ne deriva è stata finora praticamente inutilizzata, nonostante potrebbe venire sfruttata abbastanza facilmente, ad esempio con gli impianti geotermici già in funzione o quelli futuri. Impianti che, grazie alla temperatura sotterranea cittadina, richiederebbero minori profondità di perforazione rispetto agli usuali 150 metri.
ATS/dielle
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