The Gaia Centre at Delabole will close in September because of poor visitor numbers.
The £5.5m attraction was opened in August 2001 as an exhibition and education centre for green energy.
But only 20,000 people visited it in its first year and it was bought by a venture capital company.
But it has decided there are too few visitors to make the centre viable and it has submitted a planning application to turn it into an industrial unit.
Ian McIvor, chief executive investment of Surrey-based investment company Neovenator, which took over in November, said the original project was "doomed from the start" and "fundamentally flawed".
Mr McIvor said: "When we are talking about an exhibition on renewable energy it is not high on holidaymakers' list of fun things to do while they are on holiday."
Mr McIvor said his firm had invested a substantial amount of money in the centre.
"We have made a lot of improvements to the exhibition and the site in general and people that are coming there are having a better experience but there's just not enough of them coming through."