Note 9 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Deferred Tax Assets, Tax Credit Carryforwards	$ 1,437,670	$ 1,662,400
Deferred Income Tax Liabilities, Net	1,890,562	2,008,458
Deferred Income Tax Assets, Net	771,746	1,163,594
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	$ 273,936
Income Tax Examination, Year under Examination	2018 2019
Domestic Tax Jurisdiction [Member] | Internal Revenue Service (IRS) [Member]
Actual Tax Credit Recognized in Income Tax Returns			$ 659,920
Effective Income Tax Rate Reconciliation, Tax Credit, Amortization, Period (Year)			20 years
Tax Credit Carryforward, Annual Amortization Amount	$ 0	129,600
Deferred Tax Assets, Tax Credit Carryforwards, Research	$ 0	$ 990,219
Open Tax Year	2018 2019
Domestic Tax Jurisdiction [Member] | Internal Revenue Service (IRS) [Member] | Federal Energy Investment Tax Credit [Member]
Effective Income Tax Rate Reconciliation, Tax Credit, Amortization, Period (Year)		20 years
Tax Credit Carryforward, Annual Amortization Amount	$ 127,404	$ 74,265
Tax Credit Carryforward, Amount		1,892,164
Deferred Tax Assets, Tax Credit Carryforwards		655,862
State and Local Jurisdiction [Member] | Virginia, Jurisdiction [Member]
Actual Tax Credit Recognized in Income Tax Returns			$ 58,065
Effective Income Tax Rate Reconciliation, Tax Credit, Amortization, Period (Year)			20 years
Tax Credit Carryforward, Annual Amortization Amount	$ 0	$ 2,020		$ 0
Open Tax Year	2019