We hired an elite master’s Engineer (now a shareholder) to help study OTEC and heat exchange. With his help we were able to make detailed observations about the cost of an OTEC unit. The results were very exciting. We created an ‘OTEC calculator’ with all the most important variables including ammonia quantity and net power output. We are now able to create a detailed and accurate picture of the outputs and physical requirements of an OTEC unit of any size. We can even know the width of the heat exchanger for a given tube diameter and HX Duty, and how much energy will be lost pumping fluids, and the temperature of the wastewater in seconds.
Parasitic Pressure Drop.
As for water delivery, narrowing the delivery hose can massively increase the amount of energy taken by friction on the walls of the hose. On scales that are relevant to SWAC and OTEC, increasing the diameter of a hose by just 10 cm can significantly reduce the amount of energy lost to parasitic pumping.
Additional Waste heat and renewable heat.
We found recently that additional waste heat can be added to the system with additional heat exchangers and that this addition can boost power tremendously. Heat can come from motors, inverters, diesel generators, solar heaters, geo-thermal, Biomass, old-school hydrocarbons, CHP plants, process plants, etc.
Because the warm surface water is abundant, most if not all the power required to fully vaporise the working fluid can be renewable. Additional waste heat must not do the work required to vaporise the ammonia as that is already done, instead it raises the temperature and pressure of the ammonia, and this increases the net power potential of the additional heat dramatically.
This may not sound unusual, but it is. Vaporising the working fluid from a liquid to a gas requires allot of energy; up to 6MW of heating and cooling is required for 150 kw of OTEC power, once that 6MW have been added, suddenly 100 kw more heat could provide 75kw of net power. As this heat produces electrical power, the size of the condenser can remain the same. Therefore, the capital costs per kw can drop.
A new start for failed and controversial technology.
The improvement in efficiency can mean that failed or controversial sources of power such as hydrocarbons, biomass and solar-hot-water can be much more cost effective and therefore viable because they do not need to account for the phase change.
This can of course mean system and consumable efficiencies the likes of which have never before been seen. In fact, there might be no better way to use dirty fuels for heat and power because this is such an efficient process. The extra heat and pressure mean that OTEC can certainly work cost effectively in many more locations.
Sites outside the Tropics are viable for OTEC power generation all year round; this approach may produce some of the cheapest and most sustainable energy in the World. A supply of cold water is still required but this source of cold water is abundant and close to shore off the coasts of many Countries including the USA and Europe.
Use of waste heat means never before seen efficiencies and lower initial capital costs.
In being more productive per kg of water delivered, the diameter of the hoses and the quantity of water required can drop per net kw output; this can of course mean lower start-up capital costs, albeit with at least one source of additional heat and at least one additional heat exchanger. The second heat exchanger can be far smaller than the seawater heat exchangers and can sit after those; rather than heating the seawater the working fluid can be heated further instead.
Use of multi, low-, and higher grade heat sources and system carbon status.
Depending on the arrangement of the hx more than one heat source can be used in the same heat exchanger or more than one HX can be used. Use of motor heat and inverter heat as well as an extra heat source including hydrocarbons and biomass is possible. One of many glorious ironies associable with NEW-OTEC but not with higher grade heat. As a result any source of heat may come to use this system as the way it is used to generate power, and it can work in conjunction with other heat sources. The same system can offset the Co2 from any dirty consumable which may have been used, and change use of biomass from carbon neutral-ish to neutral or negative.
Hydrogen compression and storage.
An OTEC powered turbo-compressor could avoid using electricity to compress hydrogen or any other gas. Cold water could be used to cool any compressed gas. Therefore, compression and liquification of gases could be renewable.
Once compressed or liquefied a fluid can be expanded to produce power just in the same way they are in the Petro-chemical industry.
This can mean that the energy used to store hydrogen would not only be recovered, it would be gained, give or take some system losses.
Materials and relative Costs.
Heat exchangers can be mass produced already and are an established art. Heat exchangers are readily transportable in conventional shipping containers.
Up to and over one thousand times less space is required compared with solar pv farms; heat exchangers are much less susceptible to damage from natural disasters.
Different materials can offer different advantages and micro-coatings can improve heat exchanger service life and lower costs. However, the rising cost of energy and the growing desire for sustainable energy security means that the basic cost of OTEC heat exchangers system are not an eye watering expense not even when compared with mainland energy prices.
One of the most interesting aspects of deep-sea-cold-water technology is the potential to offset Co2.
Just one litre per second of cold water released for one year can have the same effect as one tree for one hundred years. Sites that can use deep-sea-cold-water can become sites for offsetting Co2. This has the potential to generate income and reduce the running costs for the user.
Deep-sea-cold-water, sea farming and biomass.
For the sea to be able to support large scale biomass projects, raising deep-sea-cold-water for the sake of bringing nutrients to the sea-surface is probably essential. The sea cannot otherwise support the growth of such a large stock. The nutrients can also be expected to help de-stress fish stocks by increase the volume of fertile sea-space and by making offshore sea-farming a real possibility.