Sunday, March 16, 2008

Thinking Bigger: OTEC Power for Lanai

This blog will have no shortage of material. Both Honolulu papers carry prominent energy-related items today about Hawaii's dependence on imported oil:

Renewable energy for Lanai is the focus of today's post and the Advertiser commentary, but before we go there, consider the last sentence in the Advertiser's editorial:

"Now the state needs to see that the money is used wisely to tap the Islands' reservoir of power -- from the wind, waves, geothermal and, of course, the sun."

That summation is why we've started this blog. Ocean Thermal Energy Conversion (OTEC) is missing from the mix -- as it nearly always is when editorial writers and reporters list Hawaii's renewable options. (Extracting electrical power from the action of "waves" isn't the same as OTEC.) And where is the "reservoir of power" in the wind? Like the sun, wind power is intermittent, and cost-effective storage of that power isn't here yet. The tropical ocean is the world's largest solar collector and storage "battery" -- so big that small thinking apparently can't detect it.

A Fossil Fuel-Free Lanai

The commentary by Castle & Cooke Hawaii's CEO Harry Saunders discusses the company's plans for solar and wind power on the (former) pineapple isle. But to "...get Lana`i powered 100 percent by renewable energy" as he suggests, they're going to need more than intermittent sun and wind power, neither of which is base load generation. Planning a future wind farm that provides 300 to 400 megawatts of power for export to Oahu, as the company did when it first announced the project in June 2007, is laudable as far as it goes, but that wouldn't be "firm power" -- electricity that Hawaiian Electric and its customers could reliably count on. Optimum power output requires optimum wind performance, and we don't have to belabor the point that the wind doesn't blow 100 percent of the time.

So even with big solar and wind farms, Lanai's going to need a firm source of renewable energy if it's to get off oil. We doubt the viability of a new crop on the island to produce a biofuel; Lanai has already transitioned from agriculture to tourism, so reversing the direction seems implausible. And transporting a biofuel to burn in a generation plant would consume fossil fuel, negating the whole intent.

The OTEC Solution

Lanai could be the perfect location for the first OTEC plant in the islands. Lanai's electrical peak demand is small, so that first plant -- perhaps only 10 megawatts -- could literally satisfy the entire electric load. David Murdock, Castle & Cooke's CEO, already is committed to wind and solar energy to reduce the island's carbon footprint, and that's fine, but those renewables won't wipe away that footprint without a trace. And until an efficient, cost-effective energy battery system is developed, he'll still have to burn something in his generators when the sun's not shining and the winds are calm. Most likely, that something will be fossil fuel.

Castle & Cooke envisions exporting large blocks of electricity to the other islands, so installing an OTEC plant a few miles off Lanai wouldn't interfere with those plans. What it would do is make Lanai the greenest island on the planet. What a vision that would be -- and what a legacy for Mr. Murdock.


DeepWater said...

All OTEC are not the same. Why some engineers like to make things more complicated, I do not know, but there is a much simpler way.
Two-phase flow of water (vapor to liquid) has the energy to do all the things desired from an OTEC process, and it does it in the most efficient way. A waterfall in the ocean to produce hydroelectricity! Mist Lift OTEC, is a "near" perpetual pumping machine, by way of two-phase flow of water, to pump deep ocean water for the purpose of electrical power generation and desalinization for drinking water.

What has been holding OTEC back all these years? It is the complications and low efficiencies and cost! A lot of water has to be pumped, I mean a LOT! These huge and power consuming pumps require lots of energy to operate besides their maintenance. Then there is the HUGE and expensive heat exchangers needed in the closed cycle approach. This keeps a lot of mechanical engineers employed, trying to design them to do the job and once done require lots of maintenance to keep them working. Are all these experts going to be around to maintain this complication? Where I live, the island of Saipan, they can not even keep diesel generators running. Getting replacement parts is a time consuming process also. It is costing $0.40 kWh for electricity on our island and we need drinking water too.

We all know that large OTEC plants are not suited for land base, due to the sizes needed to convert this thermal energy difference. They are going to need to be 'floating' plants. With the present approach to OTEC these floating or grazing plants are very expensive to build and man. Then they face the forces of nature. Ships sink! The Mist Lift OTEC 'hull' is mostly BELOW the surface of the water, thus making it less susceptible to bad weather and it does not need much personnel to operate. Concrete has a proven record to last in the ocean. Steel ships need a lot of care to last as long as concrete ones. The concrete hull is cheaper to build too. The cost of its fabrication will go down with volume of 'hulls' needed. So, let us see, mist generator, concrete hull, typical hydroelectric generator and vacuum pump. Simple! Very few moving parts or devises to maintain. Simplicity is beauty.

Two Stage Mist Lift OTEC also requires that LESS cold water to be brought up thus making the deep cold water pipe to be smaller for a same size power plant by other OTEC approaches. Also Two Stage Mist Lift OTEC comes very close to the theoretical maximum efficiency possible. So let us recap:

• No power hungry circulation pumps needed thus giving more NET electricity
• No huge and expensive heat exchanger needed (Closed cycle)
• No huge steam turbine (Open cycle)
• Less deep cold water needed to be brought up from the deep
• Less personnel to operate with less expertise
• Less susceptible to weather forces
• Less cost to build

Since this Mist Lift OTEC approach was presented to the OTEC community over 30 years ago, right at the end of funding by the US DOE, it has sat on the shelf. In these 30 years other OTEC approaches have moved at a snails pace with little forward movement. Yes, Saga University has built around 11 "pilot" plants of which none of them have been able to come to market. They are too complicated and they missed the mark. Yes, their efforts can be made useful in other areas (land based) but when it comes to doing all the 'hype' of what OTEC is possible of doing, they just have not made it happen. Mist Lift OTEC can do it!!

All that is needed now for Mist Lift OTEC to show the world its approach is better, is a second larger test. This test is needed to help in the efficient and economical design of the 'hull'. This second test will not cost much more than the first test, due to there is less unknowns. We want to study the upper end of the process (coast and condense) zone so as to better understand what is going to be needed in designing the 'hull' shape in this area.

Can you help in this effort? It is time to get OTEC out of academies hands. The Mist Lift approach does not need any NEW science or New machine engineering. All the engineering knowledge is here today and ready to go.

Here is more info as to what has been done and the math and science of Mist Lift OTEC claims.

Anonymous said...

I just found your blog. $0.40/KW in Hawaii-wow! At least oil is down a bit, but I was happy to see it up to encourage alternative energy technology like OTEC.

I just downloaded the patent for mistlift OTEC (4216657). CO2 degassing is an issue. I like the advantage of no turbine which would have to be enormous for OC OTEC. The mistlift appears an elegant solution especially if it produces desalinated water, but that would be difficult to deliver on moored sites, unless close to shore.

Bill in Costa Rica (electricity is only around $0.10 /KW)

Stuart Ridgway said...

There will be no carbon dioxide emmission by open cycle OTEC.

Stuart Ridgway