Note 8 - Common Stock and Preferred Stock (Details Textual) $ / shares in Units, $ in Millions			12 Months Ended
	Mar. 05, 2020 shares	Jan. 31, 2013 shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Common Stock, Shares Authorized (in shares)			70,000,000	70,000,000
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares			$ 0.01	$ 0.01
Common Stock, Shares, Issued, Total (in shares)			36,902,361	28,480,567
Common Stock, Capital Shares Reserved for Future Issuance (in shares)		400,000
Percentage Of Projects Annual Capacity		51.00%
Number of Milestones for Common Stock Issuance		2
Shares Payable Term From Date Earned (Year)		3 years
Water Project with Brownstein [Member]
Related Party Transaction, Expenses from Transactions with Related Party | $			$ 1.5	$ 2.3
Shares Earned Upon The Signing Of Binding Agreements [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)		100,000
Shares Earned Upon The Commencement Of Construction [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)		100,000
Conversion of Series 1 Preferred Stock in to Common Stock [Member]
Conversion of Stock, Shares Converted (in shares)			2,469
Conversion of Stock, Shares Issued (in shares)			1,000,068
Preferred Class A [Member]
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)	405.05
Conversion of Convertible Senior Notes 2020 into Preferred Stock [Member]
Debt Conversion, Converted Instrument, Shares Issued (in shares)	10,000