The following links are to various sites that discuss the alternative of energy currency, consisting of, or convertible, to units of energy. See also Digital Currency.
Energy-Backed Currencies — Proposal to denominate international trade not in dollars or other national currency, but in energy units.
Energy Standard — Proposal to denominate international trade not in dollars or other national currency, but in energy units.
Return to gold? — Argues against gold as a viable backing for currency in today's economy.