Please clarify your question,
by property do you mean property that produces clean fuel for use by vehicles?
do you mean producing clean fuel for heating or public utility use?
Do you mean hydrogen vehicles.
The tax credit is only available to the purchase of new vehicles using alternative fuels. Below is a link to the IRS web page that lists the qualifying vehicles that have been approved.
The purchase of the "unit" would be depreciable and depending on your asset acquisitions you may be allowed a Section 179 deduction. Link below.
There were credits and deductions similar to those you describe in your most recent response. However, those provisions expired on December 31, 2006. Below is an excerpt from an IRS web page (emphasis added) and a link to that page.
The maximum clean-fuel vehicle deduction and qualified electric vehicle credit were scheduled to be 25% lower for 2002 and both were scheduled to be phased out completely by 2005. The full deduction and credit are now allowed for qualified property placed in service in 2002 and 2003. The phaseout of the deduction and the credit will begin in 2004, and no deduction or credit will be allowed for property placed in service after 2006. For more information about electric and clean-fuel vehicles, see chapter 12 in Publication 535, Business Expenses..