The other day, we’re just bopping along minding our business when we happen across a sensational headline featuring the phrases “gold mines” and “geothermal energy”. It was the beginning of a rabbit hole… a rabbit hole that involves a bonified superstar of the American past, the coal mine, and our most precious resource, water. Today, many of our once bustling coal mines sit empty, gathering pools of warm water in them, just ripe for geothermal energy picking.

And it seems we have a lot of abandoned coal mines… in fact, we were shocked to find out how many. According to the Office of Surface Mining Reclamation and Enforcement (OSMRE), we’re talking about a whopper number at 48,529. While all states have some mines, most are in the Rocky Mountains, Midwest, and Appalachian Mountains. Considering that, untended, abandoned coal mines can be dangerous to public health, this could turn out to be a good thing in more ways than one.

How this works is that the deeper you go down into the earth, the hotter it gets. That means any water down deep in there is hot too. You know… on account of the fact that it’s basically on fire down there. Anyway, those mines sit abandoned gathering the hot water. That hot water, if it can be pipped up to the surface and disseminated efficiently, holds the potential to solve big energy problems. With as many abandoned mines as we have, this seems as plausible as anything else on the table.

While this isn’t a totally new idea, we now have the right combination of mounting social pressure, the right technology, and (increasingly) financial backing, to really get some things accomplished if we decide to. For example, the U.S. Department of Energy (DOE) recently announced funding opportunities for clean projects, including projects on former mine lands, to the tune of $450 million. Sure sounds like a nice little in, maybe we’ll witness the birth of a titan from one of these applicants.

There are already a few projects that have proven this can work, including Geo-Heat Center, a research and development organization with special heat-extracting technology for use in abandoned mines. It’s called the closed-loop heat pump system, and it’s supposed to be an incredibly efficient way to get the heat from the mines to the structures it’s supposed to be warming. Located in Klamath Falls, Oregon, Geo-Heat was established in 1974 by the U.S. Department of Energy and Oregon Institute of Technology to focus on the development of geothermal energy.

As the conditions continue to become more favorable, we should probably expect to see more projects exploring flooded mines for heat. It’s happening all over the place… like in the UK, where a study conducted by the British Geological Survey is saying that flooded coal mines could be used to heat up to 10 million homes there. Their study also cited the costs associated with heat extraction dropping as a factor in the ramping up of eyes on this potential energy source.

With hurdles like affordability, efficiency, and proliferation falling away, it’s certainly looking like flooded coal mines for heating might become an energy darling. It’s here… it’s in the UK, the Netherlands and Germany, it’s starting to spring up like weeds. Also, consider this… it doesn’t produce a single emission. It’s all right there… and beautifully clean. Could this be the beginning of something special? Come back next week, we’ll have more on the green tech space.