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Directory: Spindrift Hydrokinetic Energy Device
"Grid-ready and cheaper than coal"
Compiled by Sterling D. Allan
September 13, 2010
Pure Energy Systems News
The Spindrift hydrokinetic power generator is an ocean wave harnessing technology that takes advantage of the difference between wave height on the surface versus water stability deeper down. It is a buoy system that locates the alternator in the surface buoy, with a turbine down deep, by which water is accelerated via a venture shape through which the water flows.
Inventor Brian Moffat says:
- "We have designed a hydrokinetic electrical power generation device that is simple, inexpensive, low-maintenance and durable. We estimate that it will generate electricity at 1.5 cents/kWh, versus 3.0 cents/kWh for coal and 3-40 cents/kWh for existing renewables. And, this technology can scale without limit." 
- "In summary, Spindrift energy devices will have a lower capital cost and a lower power generation cost than any other power generation technology in use today. In fact, they will generate power for less than 1/2 the cost of the power currently generated by coal fired electrical power plants. Farms with Spindrift energy devices will be able to scale virtually without limit -- enough to supply most of the world's energy needs. The power generated by Spindrift energy devices will be consistent and predictable, making it suitable for base load power for utilities. Spindrift energy devices are environmentally benign." 
They've built and tested several small prototypes. The small devices are efficient - the venturi effect works in both small and large venturi tubes. 
In prototype testing, they measured an average amplification of the water speed through the venture valve at 5.18-fold for waves of just 1.5 feet in height. 
- Cost of Technologies - powerpoint slide (and an associated excel spreadsheet) (I've made the associated excel file available at the same site.)
- (YouTube; Aug. 25, 2010)
Frequently Asked Questions
The following answers were provided by Brian Moffat in the comments posted to his idea submission at the Ecomagination contest by G.E.
"The cost of interconnecting the devices into a farm is rather simple and inexpensive. A farm will utilize 2 to 3 simple "concrete block" anchors to provide "anchor points" at the periphery of the network of devices. The devices themselves will be interconnected with simple mooring and power cables. The cables between each pair of devices will be kept in tension through the use of weights and floats on the cables. In this way, the devices will be free to move but as they separate the cabling will pull them back together. As they get too close the relatively stretched cables on neighboring buoys will pull them back apart. It will be simple, cheap and effective."
Transmission of Power
"If a subsea power cable is used to get the power from a farm of Spindrift devices back to shore, then there is a significant up-front cost of about $1M / mile of cable. However, these cables are very efficient. They only lose about 3% of their power for every 600 miles of cable used. That's a very acceptable loss. And, in later deployments, we can locate farms of devices far from shore and use the power right there in the ocean to generate chemical fuels, like methanol. We could then ship the methanol back to shore with tanker ships."
Protecting Marine Life
"The water moving in and out of the venturi tube mouths is only moving as fast as the waves are moving up and down, which isn't that fast. We will also have grates across the venturi mouths to help block access to any sea life. The main thing is that since the tube is moving up and down, and since the water entering the mouths is moving rather slowly, and since the mouths will be covered by grates, it is quite unlikely that any fish, turtle or squid will get in to the device. We are as committed as you are to making sure that sea life is protected. But we also realize that right now the CO2 in the air is turning the ocean's waters acidic. That is the great danger facing many sea creatures today. If it's allowed continue, it could destroy the reefs of the world. We want to help save the oceans by replacing the burning of fossil fuels with non-polluting and renewable energy."
"Spindrift devices will handle very high wave action without trouble. They will ride up-and-down on the waves just like navigational buoys. In fact, they will keep generating power. The only potential problem would be if the wave climate grew so violent that it exceeded the limits built in to the mooring and power cables interconnecting the devices, e.g. during a "once-in-a-century" type of storm. However, this network of cables, interconnecting a farm of devices, will be made with a great enough range of dynamic tensioning so that the cabling network should survive almost any storm. But, if the limits of the network are in danger of being exceeded then the devices will be designed to automatically disconnect from each other and allow secondary cables to hold the network together. These secondary cables will be a fail-safe which will allow the devices an even greater range of motion while they ride out the storm. We would then reconnect the buoys to their primary cables after the storm is over. This would be a very unlikely event."
"The subsea power cable is expensive, at least $1M per mile, but it's also very robust and zero maintenance. Usually, the cable is buried about 6 to 10 feet beneath the sea floor. These kinds of cables have been in use for a long time, for instance, carrying power from a mainland to an island. Once they are laid down, they don't require any additional attention. The only event likely to damage such a cable is an undersea earthquake, if it causes a big shift or landslide. The other possibility is a really big ship dropping a really big anchor directly on to the cable. But these types of events are extremely rare. If a cable is damaged or broken then the cable would short out. It would cause a shutdown of the buoys (we would "turn them off" so that they stop generating power). It would require us to bring the damaged portion of the cable to the surface and repair it."
"Each device will cost about $170k and generate at least 500 kW. In terms of cost, the efficiency is a measure of how much it costs to run a technology, like coal or a Spindrift device, versus how much power it generates. Generating power with coal costs about 3 cents per kWh because the cost of maintenance and fuel cost about 3 cents for every kWh of energy produced. Spindrift devices have very low maintenance and operation costs because they are so simple, i.e. there isn't much needed in the way of monitoring or maintenance, and the fuel (i.e. the energy in the waves) is free. So, it turns out that Spindrift devices can generate power for quite a bit less than 1.5 cents per kWh."
"We estimate that the annual operation and maintenance costs will be about $29k per device, or about $58 per kW."
"Spindrift devices would survive an oil spill and continue operating normally. Oil in the water would have no detrimental effect on Spindrift devices at all."
"Our economic analyses, and the fact that Spindrift devices will be so inexpensive, suggest that it will be advantageous to populate each farm with more devices than will be needed to maximize the bandwidth of the farm's associated subsea power cable(s) most of the time. This will allow each farm to continue generating power at its maximum, i.e. at its "rated", level even when wave heights fall below the minimum optimal height. Another consequence of this surplus capacity will be that when a Spindrift device will need to be replaced, the farm's output will likely remain at its maximum power level - essentially the "offline" device will simply reduce the farm's surplus capacity. We also expect to be able to replace a device in a single day."
"Desalinization of seawater is a great application for the Spindrift Energy devices. For this application we could locate a farm of Spindrift devices pretty far from shore and use the power locally (at sea) to desalinate seawater. The purified water could be put directly into a tanker stationed on site, or into large floating plastic sacks (NASA is actually doing something along these lines using algae). We could frequently bring the fresh water back to shore. This frees up the buoys to work without a subsea power cable, which is really nice."
"Cavitation may be a problem. These devices will be accelerating the seawater to a speed close to, and sometimes reaching, the "choke speed" of the water. Cavitation will occur just before the choke speed is reached. As a result, it may be necessary to swap out turbines every few years - we'll have to see. However, this kind of "grand overhaul" every few years is already factored in to our cost estimates. Also, the turbine we'll be using is a "bi-directional" turbine. No matter what direction the seawater comes from, the turbine will turn in the same direction. These types of bi-directional turbines are already used in oscillating water columns. However, we have a custom (i.e. a better) design for our wave energy devices."
"Any point absorber wave energy device extracting power from waves will have a phase latency. The other way to think of this type of wave energy device is to imagine that it's a 'wave dampening' device - that its purpose is to suppress waves. From that perspective, it's easier to see that the device must move out of phase with the wave. Also, the buoy's drag would affect the buoy's range of motion (and therefore its speed), but the power available for extraction from the water moving through the venturi tube throat is correctly specified by the equation shown."
Profile: Spindrift Energy
As of Aug. 25, 2010, the technology is in the early stages of development. The company is not yet incorporated, and is self-funded. They plan further modeling and prototyping to continue validating and refining this technology.
"We believe we have a disruptive, clean energy technology with a potential to change the world for the better."
Profile: Brian Moffat
"I worked at Google for almost 4 years, and Google is patenting one of my inventions. I worked at Disney Imagineering. I have several patents pending. I am an alumnus of UC Irvine. I want to help save our environment." 
Top 100 Assessment
On Sept. 14, 2010, inventor Brian Moffat presented the first draft of the following document for consideration by the New Energy Congress, which has included it in their list of Top 100 Clean Energy Technologies, based on a 1-10 ranking for several factors in Ten Criteria. The following is an updated revision presented on Sept. 21, 2010. A Word doc version of this can be downloaded here.
Submitted by: Brian Moffat
Company name: Spindrift Energy
Product / Technology: Hydrokinetic wave energy device
- 10 Sustainability
- 10 Replenishability
- 10 Feasibility of recycling of components composed of rare elements
- 10 Non-depleting energy source
- 10 Ubiquitous energy source
II. Environmental Impact
- 10 Containment
- 8 Duration
- Expected lifetime of device is 20 years. The only moving components exposed to the seawater will be part of a shaft and the turbine. They’ll be protected from corrosion by an “impressed current”. Cavitation may require replacing the turbine blades every 10 years.
- 10 CO2, NOx and other emissions
- 10 EMF radiation
- 10 caustic, toxic, poisonous
- 10 noisy
- 10 smelly
- 8 strip mining, scarring of land
- Each device is constructed mainly of concrete. About 1 ton of steel. One alternator (some steel, copper, etc.).
- 9 impact on animals
- The rate of water flow at the venturi mouths oscillates between 0 and 3 m/s. But it reverses about every 4 seconds. Most swimming animals should either be stopped by the grates, or be able to swim out of the mouths. Only small, slow animals (e.g. baby jellyfish) at depths of about 50 and 150 feet should be vulnerable.
- 8 visual impact
- Some initial farms may be located tens of miles from shore, and tops of buoys may be visible from land. Later deployments will be hundreds of miles from shore – no visibility.
III. Cost (cents / kwh)
- 10 Device cost
- Each 500 kW device will cost about $170K, device capital cost of $340 / kW. Lower than any other power technology.
- 8 Manufacturing and marketing costs
- Manufacturing is primarily of concrete shell of buoy and tube. Low marketing costs – mostly long-term power-purchase agreements.
- 4 Pre-construction costs including studies and obtaining permits
- Permitting costs likely to be high – unless government streamlines process at some point in the future.
- 6 Installation / construction costs
- Near-shore installations that use subsea cable will incur cost of about $1M / mile to purchase and install cable. Installed capital cost for farm of 100 devices, 20 miles from shore, is expected to be about $1,000 / kW.
- 7 Commissioning and testing costs
- Devices will be tested at shore. Cost of “plug-and-play” installation into farm grid expected to be low on a per-kW basis.
- 10 Fuel costs
- 9 Servicing / Maintenance costs
- Expected to be $58 / kW / year. Critical portions of venturi throat are self-cleaning due to frequent, rapid surges of seawater. Steel components protected by impressed current. Most significant potential maintenance cost is replacement of turbine blades every 10 years if cavitation is more of a problem than anticipated.
- 9 Replacement parts costs
- Entire devices can be replaced at a cost of $340 / kW. And, only 3 moving parts.
- 7 Decommissioning and disposal costs
- Any un-salvageable devices will be stripped of their moving parts (alternator, shaft and turbine), and their other electronic components, and likely sunk to create artificial reefs. Cement is a good surface for such reefs.
- 10 Environmental costs
- Each device is expected to displace between 28 to 54 tonnes of CO2 (depending on fossil fuel displaced) over its 20-year lifetime.
IV. Credibility of Evidence
- 8 Is the underlying principle sound?
- The only element of the design not proven in other contexts was the venturi tube when driven by an oscillating and accelerating pattern of water flow. A sea trial showed that the tube worked beautifully when driven by ocean waves.
- 2 Is it well proven?
- Limited data from one sea trial, and many tank tests, which indicate that venturi tube will work as expected.
- 5 How much data are there to support the underlying principle?
- The data is limited. However, data do suggest that the device will accelerate water through the venturi tube. And, the technologies to extract that power are mature.
- 3 How solid is the extrapolation to full optimization?
- 1 Number of independent replications?
- One sea trial validation of venturi tube.
V. Stability / Reliability
- 8 Device performance
- Each device has only 3 moving parts. The turbine should be reliable –the turbine is bi-directional and has articulating blades but is completely passive. The resistance of the alternator to turning, and the smoothness of its turning, will be controlled dynamically by controlling the current through its field coils.
- 9 Life expectancy
- Expected life of each device is 20 years. Concrete shell of buoy and tube should be long-lived. Alternator should last 20 years. Corrosion will be prevented with impressed current to all vulnerable components. Possible that turbine blades will need replacing every 10 years.
- 8 Energy source availability (24/7/365)
- Analysis of historical wave data from NOAA buoys (up to 20 years’ worth per buoy) indicates that Spindrift devices would have capacity factors of about 90%.
- 10 Manufacturing logistics (feasibility)
- Creating concrete shell of buoy and venturi tube very similar to methods used to create concrete barges (boats). Manual of construction techniques available from United Nations source.
- 10 Scalability
Because they can operate in the deep sea, farms of Spindrift devices can scale virtually without limit. In the deep sea, electrical power would likely be used to create chemical fuels (e.g. methanol) on site. These would then be shipped to shore in tankers.
- 10 Production of scale (low and high feasibility)
- 10 Resources required – materials and tooling availability
- Simple technology, simple materials, simple tools.
- 8 Ease of installation
- Installation of subsea power cable, for near-shore installations using such a cable, is most difficult part. Cost of cable and installation is about $1M / mile.
- 7 Applicability
- 7 Serviceability
- 8 Decommissioning
- Likely to be rather simple. Remove alternator. Remove shaft and turbine. Tow buoy-tube concrete shell to appropriate location. And, sink it, to create an artificial reef.
VII. Safety / Danger to persons
- 10 Explosive
- 10 Could it be modified into a weapon of mass destruction?
- 8 Electrocution hazard
- Likely to generate high-voltage (at least when sending to shore via subsea power cable). That, plus wet conditions, creates risk for electrocution. Care will be needed.
- 10 Irradiation, etc.
- 10 EMF radiation (non-ionizing)
- 10 Noise
- 10 Vibrations
- 10 Environmental emissions
- 10 - during operation
- 10 -output to environment
- 10 - input fuel source
- 10 - components
- 10 - manufacturing / installation / servicing
- 10 - transport of fuel
VIII. Politics of science
- 8 Encumbrance
- 9 Key personality and associates
- 10 Motivation foundation. “Continuum of greed” to “Good of humanity”
- 8 Involved team – primo talented, experienced, team compatibility
IX. Open-source conducive
- 7 Unambiguous plan publication… any commercial applications must be licensed.
X. Stage of device development
- 3 Stage = one stable prototype [of venturi tube]
In the News
- Top 100 / Feature: Hydro > Ocean Wave > Buoys >
Spindrift Hydrokinetic Energy Device - This ocean wave harnessing technology takes advantage of the difference between wave height on the surface versus water stability deeper down. It is a buoy system that locates the alternator in the surface buoy, with a turbine down deep, by which water is accelerated via a venture shape through which the water flows. (PESWiki; Sept. 13, 2010)
Dealing with brine
On October 04, 2010 8:13 PM mountain, Michael Riversong wrote:
Went ahead and voted Spindrift as a T50 tech. For some reason i'm not a big fan of ocean energy devices -- mainly because the materials that have to be used are not that well established. We always tend to underestimate what brine can do to metals and plastics.
They mentioned using a venturi tube for part of the effect. That's kind of cool. Perhaps this idea should be taken a step further, and a vortex of some sort should be developed in the device. This might have some side effects in terms of changing the way corrosion works too.
Right now i'm developing a short course in Vortexian Mechanics. A colleague in Finland took some great photos at the Schauberger Museum and has given me permission to link them. Comments on any of the courses, which are being made available online, and always welcome. Will post separately about those soon, in the Forum.
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- Directory:Low Impact Hydro
- Directory:Ocean or Marine Power
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