The Isle of Man government has recently published a report produced by Aquatera Limited on the viability of various forms on renewable energy for the Island. The report available at:
http://www.gov.im/dti/Energy/
broadly concludes that Wind Power is the only viable resource in the near term using existing technologies. Moreover, analysis of the economics of an offshore resource details that the resulting revenue from such a project would repay the initial set-up and running cost after 13.73 years. Hence, such a project would only provide an internal rate of return of 5.1756% over 13.73 years. With the 10 year Gilt yield being around 4.82%, such a project (in my view) is not financially justifiable since its return over gilts is not enough to justify the inherent risk of such a project.
What about Onshore Wind Farms?
The report unfortunately makes no real attempt to explain why the much more obvious options of an onshore wind farm were not considered. In fact, the option of an onshore wind farm seems to have been discounted from the start, with the rationale given on page 47:
Due to the structure of the Manx planning process, the possibility for commercial scale onshore wind turbines has already been discounted.
Moreover, within the 143 page report the only other reference’s on commercial scale onshore wind farms is on page 18, which reads:
Onshore wind was specifically excluded from this report at the request of the DTI, as previous studies have already looked at the opportunities for this technology.
and on page 15, I found:
In the case of the Isle of Man there are some specific legal protection mechanisms that make onshore development of renewables particularly challenging.
Financial case for Onshore Wind Farms
Though the figures where not worked out for an onshore wind farm, after doing I little digging I found within the article ‘Land- vs. Sea-based Wind Farms’, at:
http://www.pbs.org/newshour/science/wind/landvssea.html
the following guidelines:
Cape Wind itself has an expected energy output of 38 percent of capacity over the course of a year, compared to the mid-to-high 20s or low-30s for onshore wind farms, noted Cape Wind’s communications director Mark Rodgers…
But one of the main challenges to building offshore is cost. The price tag of installing offshore sites can reach 50 percent to twice that of land-based wind technology, Calvert said
Hence, as an estimate I would suggest the drop in power of an onshore vs offshore site would be around 18%, but the reduced cost on an onshore vs offshore farm would be between a 1/3–1/2. Therefore, the cost per KWH would be reduced by 21% - 41% over 13.73 years. Implying an internal rate of return of 6.26%-7.30%, which would provide a return over gilt yield’s in proportion to the level of risk taken by the investor.