The future of energy generation.

China is the latest country to take on the decades-old challenge of generating electricity from the world’s oceans. Beijing has invested an estimated $160 million in tidal and wave energy projects since 2010, the Wall Street Journal reported, embarking on joint ventures with Lockheed Martin, Israel’s Eco Wave Power, the Netherlands’ Arcadis and Singapore’s Atlantis Resources to build varied projects along the country’s 17,700-km coastline.

Harnessing the power of tides and waves and transforming it into kilowatt hours or stored electricity has been the life-long holy grail for a small and dedicated group of investors, engineers and entrepreneurs, many in the US and Europe – so far with limited success.

Their quest has been to create a machine that’s tough enough to withstand the constant pressure of surging water, yet sensitive enough to harness that power for electricity, all while being unobtrusive enough not to disturb marine life, commercial fishing or recreational water sports. The result – some unwieldy-looking mechanical beasts, like the “SeaGen” installed off the coast of Ireland, one of the few commercial scale marine energy plants:

China’s ocean energy plans are ambitious, and more disruptive. They include massive T-shaped underwater “dynamic tidal walls” 30 kilometres long along the coast, particularly in the Yellow Sea between North Korea, South Korea and China, which the Wall Street Journal says could generate as much energy as two nuclear power plants and cost $30 billion. They’re not unobtrusive – an early research paper on these walls notes they rely on “actively interfering in specific regional dynamic tidal systems”. China is working with Dutch companies like Arcadis who have previously developed tidal walls to keep water out of the Netherlands sea-level settlements. Here’s how it works:

Ambitious plans for ocean energy plants have rarely run smoothly – China installed dozens of tidal plants in the 1960s and 1970s, most of which are defunct now. More recently, the “Pelamis wave energy machine,” named after a species of sea snake, dates back to 1998, though the first prototype didn’t appear until 2004. Three Pelamis machines were deployed off of Portugal in September of 2008, but the project was iced two months later, because of mechanical problems and after the project’s owner, investment bank Babcock & Brown, went into liquidation.

Now the Pelamis is testing a “second generation” machine for energy giant E.ON off the coast of Scotland.

A tidal project in Eastport, Maine, which has advocates dating back to US president Franklin D Roosevelt, finally became a reality in August 2012, when a turbine “eggbeater turned sideways” was lowered into the water.

While surging water loosened bolts and caused other mechanical problems and delays, the turbine did generate enough energy to power 25 homes and an additional turbine will be added this year.

Despite the delays and setbacks, the money keeps flowing in to ocean energy research, and not just from China. Private investment in European ocean and wave technology energy ventures was about $825 million over the past seven years, the Wall Street Journal reported. In August of last year, the US Department of Energy said it would invest about $16 million in projects on US coasts and waterways.