Lion Solar Thermal Technology
Lion Alternative Energy Plc (Lion) has developed a number of technologies which combined will allow the low cost production of energy from renewable resources.
The Power Industry
Although representing under 20% of total energy used, electricity is the energy carrier of choice for world economies and the generation and distribution of electricity is world’s largest business with annual revenues of over USD 1,200 Billion and with an expected continued growth rate of 2.1%.
The energy industry has been dominated until now by vertically integrated monopolies. The governments have been profoundly involved in the energy business as owners of distribution grids and power plants and as policy makers they have had a controlling role in promoting technologies through regulations or subsidies.
The solution advocated for the transportation and delivery of electricity has been the “smart grid”, an aggregate of networks and power generators supposed to deliver electricity to consumers using digital technology. According to its proponents the smart grid will reduce the amount of required stand-by spinning reserve, as the load curve will level itself through the operation of the invisible hand of free-market.
The smart grid is also supposed to resist terrorist attacks and be able to heal itself. But actually, the potential paralyzing effect caused by solar storms or Electromagnetic Pulses (EMP) generated by nuclear explosions or modern electromagnetic weapons is well known. The “smarter” the grid, (by inclusion of computer-controlled circuits, relays, sensors etc.) the more vulnerable to EMP and the increase in complexity reduces the grid security. Also, certain groups or countries have currently the capability to shut down power grids through cyber attacks.
The final solution to power delivery is decentralized power generation combined with power storage. Distributed generation allows independence from grid failures and price fluctuations, at the same time reducing generating and transportation costs at the regional and national level. The current global trend is towards distributed generation and towards sustainable technologies based on clean, renewable resources and we are likely to witness the implosion of the centralized utility. The ongoing deregulation trend will allow independent producers to compete in the open market and promote a reduction of the energy costs. In order for the market forces to be effective, the new independent producers will need access to new low cost forms of energy storage and transportation.
Lion is well positioned for these changes, since it can produce electricity from non polluting, renewable resources at costs below the current costs of power produced by fossil power plants and it can pursue distributed generation independent of the grid due to its low cost energy storage solutions. The size of the Lion Solar Power Plants can range from 5 KW to utility scale, so Lion could cover any regional, local or individual user energy applications.
Existing Solar Technologies
The advantages of solar over other power generating technologies are multiple (most obvious being the ubiquitous, free and unlimited fuel) and the reasons the solar technologies have not proliferated faster are economic (still in most areas higher cost than fossil fuel based technologies) and output intermittence. The trend is though for a continuous decrease in the cost of solar technologies which is approaching grid parity while the cost of fossil fuel based technologies has not seen an important reduction. The Lion solar thermal power plants will have a continuous power output at a cost below the cost realized by the existing fossil fuel and renewable technologies.
Solar technologies have two major classifications: thermal (to which Lion belongs), which use the thermal energy contained in solar radiation, and photovoltaic (PV), which convert into electricity the energy inherent in solar photons.
Competition – Solar Photovoltaic (PV) Technology
Most of the recent progress in performance and production in the solar industry has been concentrated on PV systems. Over the past 30 years, the levelized cost of PV electricity (LCOE) has fallen by an average 10% each year and the PV solar power industry has already achieved grid parity in some areas under the pressure of lowering feed-in tariffs and based on new lower cost technologies and equipment.
The range of solar cells is becoming more diverse: in addition to crystalline, amorphous and multi crystalline silicon cells, various thin-film technologies are now available A larger proportion of the light spectrum can be absorbed: multiple cells use several spectral ranges and convert a correspondingly higher proportion of the incident light into electricity.
Established silicone PV cells are classified as crystalline ”thick-film” and “thin-film”. Newer technologies include high efficiency multi-junction cells used in concentrating PV systems, with overlaid thin layers (gallium arsenide, cadmium telluride, copper indium selenide, germanium, etc. each for a different band of wavelengths) and CIGS cells (Copper, Indium, Gallium and Selenium).
Crystalline silicon solar cells (cSi) achieve the highest efficiency (20%), however the manufacture of high-purity silicon requires relatively large amounts of energy and implied higher costs.
Thin film modules generally made from amorphous silicon (a-Si) make better use of sites with diffuse insolation due to cloudy weather where the short and medium-wave range of the solar spectrum are predominant. They can absorb light considerably better than crystalline silicon (that is why a 1 ìm film thickness is sufficient), however, their efficiency is substantially lower (6 – 9%). Cadmium telluride (CdTe) is currently the most economic thin-film technology. CdTe modules have a relatively high efficiency (11%) and are being manufactured in high quantities at reasonable cost. But recently the crystalline silicon technology is increasingly catching up due to the efficiency factor.
Conserving silicon is the top industry priority and the wafers used to manufacture cells are becoming thinner. Even with thinner cells, the production of silicon by melting quartz sand at very high temperatures uses a lot of energy. New fluidized bed reactor technology has lowered production energy requirements but caused a similar material losses.
Module efficiency determines PV plant sites requirements: in the case of crystalline modules, 10 – 15 m2 are needed for an output of 1 kw peak (kWp), whereas for thin-film modules the area would be 15 – 25 m2 .
Developing PV Technologies
Concentrators use mirrors or lenses to focus light on to high efficiency multi-junction cells and use heat sinks or active cooling to dissipate the large amount of heat generated. They claim higher overall efficiencies and their site requirements are lower than for the other PV technologies.
Dye-sensitized solar cells are photo electrochemical systems based on a semiconductor formed between a photo- sensitized anode and an electrolyte. They are made of low-cost materials and do not need complex production. Their efficiency is less than that of thin-film cells, but their performance price ratio is favorable. Commercial applications are still held up due to long term chemical stability challenges.
Space solar power stations (an older concept from the 70’s), pursued by NASA, Boeing and the Japanese Space Agency until now are cost prohibitive. In the NASA version, “Suntowers” in geostationary orbits 37,000 km above earth are supposed to use mirrors to reflect sunlight to a string of high efficiency conversion solar cells. Transmitters then beam down the electricity to power storage facilities on earth as microwaves. The continuous output advantage of the technology is offset by possible vulnerability to terrorist attacks.
The large scale proliferation of PV systems could raise environmental issues (due to the toxicity of many materials used in the production of the PV modules) and could create possible raw materials shortages. For now and the near future, the PV panels use costly and complex manufacturing processes and materials which present a challenge in the last life cycle of the technology, the recycling.
Existing Solar Thermal Technologies
Solar thermal systems collect the thermal energy contained in solar radiation. All currently developed solar thermal technologies referred to as Concentrated Solar Power (CSP) concentrate in one form or another the solar beam radiance using reflectors / mirrors in order to increase the energy density. For this reason, they can use only beam radiance with a high level of Direct Normal Irradiation (DNI) of over 1,800 kWh/m2/year (2,500 kWh /m2/yr recommended). That is why all CSP technologies are latitude dependent and they do not perform well in cloudy weather. This requirement limits the geographical areas where CSP is efficient to: Southern Europe; Middle East; North Africa; Southern Africa; Some regions in India; North-western and central Australia; South- Western USA; Northern Mexico and the Andean Plateau. Ideal locations are higher elevations, where DNI is significantly higher and absorption and scattering of sunlight due to aerosols can be much lower.
All existing CSP technologies are thermal processes which in the 1st stage heat a fluid. The heated fluid generates then through a thermodynamic cycle (Rankine, Brayton or Stirling) mechanical energy which is converted into electrical power by an alternator. Currently, there are four developed solar thermal technologies: Trough, Fresnel, Tower and Dish/Engine. The Trough, Fresnel and Dish are referred to as distributed systems (collect the energy at multiple field points), while the Tower is a central receiver. Of the three, the Trough, Fresnel and the Tower are currently in commercial use (4.2 GW capacity parabolic troughs, over 6820 MW solar power towers, 177 MW Fresnel). Fresnel is the simplest and the lowest cost of the three.
Parabolic trough shaped mirror reflectors are used to concentrate sunrays on to receiver tubes placed along the trough focal line. In these tubes a thermal transfer fluid (usually oil) is circulated and heated up to 500iC, and then pumped through a series of heat exchangers to produce superheated steam. As an alternative, the steam could be generated directly in the field tubes, eliminating the heat exchange stage and reducing costs. The steam is converted to electricity in a conventional steam turbine generator, which could be integrated into a hybrid combined steam and gas turbine cycle.
Linear Fresnel Concentrators
The Fresnel collector consists of parallel rows of modular flat mirrors, which concentrate beam radiation to a stationary receiver at a height of several meters. This receiver actually contains a second stage inverted reflector which further concentrates the radiation to an absorber tube. This not only enlarges the target for the Fresnel reflectors but additionally insulates the absorber tube. The site required is reduced to half the size of a trough site, due to the reflectors bing placed next to each other.
Central Receiver/Solar Tower
A circular array of heliostats (individually-tracking mirrors) is concentrating sunlight with 0.1% angle accuracy on to a central receiver mounted at the top of a tower. A heat transfer medium absorbs the highly concentrated radiation and converts it into thermal energy used in the subsequent generation of superheated steam for turbine operation. Heat transfer media used include water/steam, molten salts, liquid sodium and air. If a gas or even air is pressurized in the receiver, it can be used alternatively to drive a gas turbine (instead of steam being produced for a steam turbine).
A parabolic dish-shaped reflector is used to concentrate sunlight on to a receiver located at the focal point of the dish, enabling the fluid in the receiver to be heated to approx. 750iC and then used to generate electricity in a small Stirling engine, or a micro turbine, attached to the receiver.
New solar thermal concepts under development include Solar Chimney, where the sun heats air beneath a gigantic, greenhouse like glass roof, the hot air rises in a tower and drives the turbines. Solar chimney claim to convert an average of 45% of the solar radiation falling down on the collector area into heat. A theoretical expansion of the concept (using solar or alternative heat sources) could be Atmospheric Vortex where a cylindrical wall open at the top creates a controlled tornado which continues beyond the limits of the cylinder (in theory to the top of troposphere), attempting to capture the mechanical energy that would be produced if a mass of air were raised reversibly from the bottom to the top of the troposphere.
Advantages of the Solar Thermal Over PV Systems in General
Even if recent continued cost reductions in solar PV technologies components have made them more cost competitive than solar thermal technologies, the existing CSP technologies (Concentrated Solar Power) maintain in general a number of important advantages over the solar PV systems:
– They can be operated in cogeneration systems with increased (up to 55%) total efficiency.
– They are suitable for hybrid operation either by the solar plant using complementary heat sources for continuous output in the absence of sun (SEGS) or by the solar plant providing supplemental heat to bottoming cycles of combined cycle gas plants (ISCCS).
– They can be used in desalination systems. (Currently solar distillation is not yet price competitive but the Lion desalination technology allows the production of distilled water at competitive prices).
– They can incorporate short term thermal energy storage which increases their dispatchability potential, as opposed to the PV systems for which there is no economical electrical energy storage solution yet.
– The production of CSP components does not use in general toxic substances. PV modules production uses acids and solutions to etch the silicon wafers, can use explosive or poisonous gases (silane, phosphineis) toxic substances (cadmium) and polluting substances (1Kg nitrogen trifluoride or sulfur hexafluoride has the effect of 20t of carbon dioxide if released into the atmosphere). In general the PV modules manufacturing generates a toxic industrial effluent and hazardous gases which require complex technologies for their disposal.
– The product end of life recycling stage presents a challenge for the PV panels manufacturers. Various technologies have to be employed to burn the composite plastics, to remove the cell metallization and doped films and to separate the string connectors. The recyclable materials cannot be reused by the solar industry but only to make recycled glass.
– The production of CSP plants components is less complex than in case of PV and the equipment production plants require less capital to build and are easier to deploy.
– They use raw materials that are available worldwide and not exposed to shortages: steel, glass, concrete, malten salt (or polymers in case of Lion) .
– The materials used for the CSP heat agent conduits are available in large quantities (even low cost recyclable polymers as in the case of Lion) while the electrical conduits connecting PV panels depend on the metals market and a large scale technology proliferation could lead to copper scarcity.
– New PV modules are using rare materials (ex. indium, gallium, etc.) Rising metal prices are prompting manufacturers to use aluminum or copper in their metallization pastes instead of expensive silver.
– CSP systems have a 4 months (less than 2 months in case of Lion) energy amortization time (the time the system needs to recover the energy used to produce its components, for operation and for waste removal). By comparison, wind power amortization time is 4 – 7 months, hydro power 3 – 9 months, polycrystalline silicon 2 – 5 years and power plants based on exhaustible fuels (coal, gas, nuclear) can never amortize the energy expended, because they always need more fuel than the energy they produce.
For the solar thermal technologies to be competitive in general, they need storage. They could substitute then coal as baseload source. Large-scale CSP with thermal storage can be cheaper than large-scale PV with battery storage. The Lion technology will allow the production of electricity in fully dispatchable solar thermal power plants at costs below the cost of electricity generated by PV solar plants or fossil fuel plants.
Solar Thermal Technology Trends
According to ESTELA, (European Solar Thermal Electricity Association), only a moderate reduction (2 – 5%) in the levelized cost of energy (LCOE) can be expected based on the economy of scale within the existing CSP technologies. Further technological improvements are needed for CSP to reach higher performance: increased operating temperature, increased energy storage and reduction in water consumption.
There are currently two possible pathways considered for further development of the existing CSP solar thermal power technologies: hybrid operation and addition (or expansion) of thermal storage.
In new forms of hybrid operations Integrated Solar Combined Cycle (ISCC) plants, the CSP section (Concentrated Solar Power) is used to supplement the waste heat recovered from a gas turbine to be used in a steam Rankine bottoming cycle. Studies have shown that combined efficiency could be improved and operating costs reduced by as much as 22% compared with gas plants of similar size. Due to technical reasons, the CSP (solar) fraction of the ISCC plants is limited to one-third, which translates into 15% of the total power production capacity of a combined-cycle plant.
In hybrid Solar Energy Generating Systems (SEGS) an adjacent fossil plant component is used during cloudy and stormy phases providing thermal energy during breaks in radiation with a contribution limited to 25 % of annual power generation. The SEGS plants are used for peak load applications while the ISCC plants (with 30 – 40 Mwe capacities) for mid-load to base-load operation.
The solar thermal plants market could broaden with the use of thermal storage providing around the clock operation by the expansion of the thermal storage capacity from 2000 to 6000 full load hours per year. The low efficiency of the technology (15% as of now with 20% as future goal), the high cost of the additional troughs and the additional site required, would make this for the near future challenging economically.
Solar Thermal Technology is expected to achieve in the medium term a substantial status alongside current market leaders hydro, wind and solar PV. According to the German Aerospace Center (DLR), CSP has a world growth potential of 40 GW by 2030 and ESTELA estimates the growth to 60 GW by 2030 only in Europe. The IEA CSP Technology Roadmap suggests that in the sunniest countries, CSP can be expected to become a competitive source of bulk power in peak and intermediate loads by 2020, and of base-load power by 2025 – 2030. As a dispatchable source CSP is more valuable than traditional baseload power.
Solar thermal power plants to be located in north Africa or Middle East (MENA) could play an important role in the future providing energy for Europe. The gigantic solar radiation resources in the area are several orders of magnitude larger than the global energy demand. Bulk solar thermal power could be transferred to European utilities grids for consumption in Europe at a low cost (2 ¢/KWh) from great distances (2,000 – 3,000 km) using existing state-of-the-art low loss bulk power transmission technology (High Voltage Direct Current – HVDC). The DC current transported in this method with low transmission loss (10-15%) is then reconverted to alternating current at the receiving station. Electrical energy of up to 3,000 Mwe can be transported this way for long distances. With this goal the Trans-Mediterranean Renewable Energy Cooperation (TREC) was founded by The Club of Rome, the Hamburg Climate Protection Foundation and the National Energy Research Center of Jordan. Together with the German Aerospace Center (DLR) they have developed the DESERTEC Concept proposing that Europe and MENA cooperate in the production of electricity and desalinated water producing CSP clean electrical power in the MENA deserts that can be transmitted via HVDC transmission lines to Europe.
Unlike other renewable technologies which might grow gradually, in solar thermal technologies a breakthrough is needed and the associated R&D expenses needed for this may limit the competition to well funded companies. Lion has completed with own resources the 1st R & D stage for its high efficiency low cost solar thermal power plant concept and is well positioned to deploy assembly plants for components and build its solar thermal power plants and proprietary desalination systems once the political climate in the MENA region will allow the implementation of the DESERTEC program.
Advantages of the Lion Technology over the existing CSP Technologies
In addition to low cost (under $1,000,000 / Mw including energy storage for continuous output) the Lion solar thermal plants have further specific advantages over the existing CSP technologies:
– The central equipment of the Lion plants, the Electrochemical Thermal Converter (ETC) has a 65 – 75% thermal /electrical conversion ratio surpassing the Carnot cycle limitations (theoretical efficiency limit for the conversion cycle of thermal energy into work) while the average fossil fuel plant converts 36% of the input thermal energy into electricity and the existing CSP plants have an efficiency of 15% (with 20% future goal).
– The ETC operates with 70oC – 100oC input temperatures and normal pressure while all existing thermodynamic cycles (Rankine, Brayton or Stirling) require higher temperatures (300°C- 500°C). This is important since thermal losses by radiation increases by the 4th degree of the absolute temperature which leads to 30% – 40% losses in case of medium temperature cycles and in high temperature cycles they could approach the value of the entire heat energy collected from the sun. The Lion low operating temperature allows the use of polymer for collectors, heat agents conduits, thermal storage, heat exchange, ETC stacks, avoiding the high costs related to special materials required by existing CSP operating at high temperatures (up to 700oC) and pressures (120 bar).
– The Lion collectors absorb both beam and diffuse solar irradiance. Since they are not concentrating the solar radiation and are not dependent on high level direct normal irradiation as in the case of CSP plants (which require over 1,800 kWh/m2/yr direct normal irradiation) the Lion solar plants could function at various latitudes.
– The high efficiency of the Lion technology leads to total collector surface and site economies. Assuming an 80% system ground coverage ratio (collector surface /plant site) and 1,000 W/m2 solar irradiation, the site requirements for an Lion plant would be 0.5 Ha/MW (including the site allocation for stored energy production), an important feature in case of expensive coastal area sites or competition with agriculture land.
– The Lion solar power plants generate continuous power output due to the combined short term thermal storage (10 hours) and long term flow battery (or hydrogen storage in case of large plants). The Lion specific cost for adding energy storage is lower than the cost for adding T&D infrastructure (which could run up to $1,400 / Kw), due to a large extent to the low cost Lion collectors. The Lion plants are fully dispatchable (can be dispatched at the request of grid operators on demand), reliable and stable for utility applications. The Lion energy storage increases plants’ annual capacity factor to 90% (while the existing CSP plants have 20 – 45% capacity factors).
– Water availability for cooling, steam generation and cleaning of reflectors (6m3 /MWh) is a prerequisite for CSP plants, which is a challenge since due to the direct radiation requirement CSP plants are located in arid areas. The Lion solar plants have low water consumption (just for cleaning the polymer collectors).
– The collectors field (largest capital item representing 43 – 60% of total costs in CSP systems) represents only 10% of the total cost of the Lion solar thermal plants. Since the tracking precision is not critical and if the site permits, additional low cost collectors could be added to compensate for the absence of tracking while CSP plants require complex tracking installations designed to maintain precise direct beam angles. The polymer collectors are easy to replace and require less maintenance while the CSP technologies are using high quality reflectors and vacuum tubes receivers requiring metal/glass junctions dilatation management and causing production interruption when replaced. The Lion collectors have low reflectivity preventing interference with the air traffic and their low temperature do not pose any potential danger to birds.
– There are no components using toxic materials or requiring toxic production processes in the Lion systems. Most of the components of the Lion plants are recyclable, which reduces their life cycle costs.
– The Lion equipment assembling plants could be deployed in short periods of time in the proximity of project areas. The Lion solar thermal power plants could be assembled in shorter periods of time (under 1 year) than CSP plants. Lion systems have modular flexibility – from 5 Kw to hundreds of MW while the existing CSP systems require large applications.
The Lion Solar Thermal Power Plant
1. The process starts with the absorption of the solar radiation and its conversion into thermal energy by the Lion proprietary polymer Solar Thermal Collectors which heat water to 70°C – 100°C with a solar / thermal efficiency of 75%. The collectors can absorb both beam and diffuse solar irradiance (coming from all directions) so they can function at various latitudes. The total active surface of the collectors field is sized to generate sufficient thermal energy: 1) for electricity direct consumption 2) to be stored as thermal energy in the thermal accumulator for 10 hours operation 3) to generate electricity to be stored in the flow battery for longer periods and 4) to produce electricity for the electrolysis of hydrogen (for large applications). They could be set at a fixed tilt angle (equal to the site latitude) or, in case of site limitations seasonal repositioning or one direction tracking could be used.
2. The heated water is circulated continuously to the Lion short term Thermal Energy Accumulator which is sized to store enough thermal energy for up to 10 hours electricity output. The proprietary Lion thermal storage has reduced losses from convection and radiation.
3. The thermal energy in the thermal accumulator is continuously transferred by a proprietary Polymer Heat Exchange system to the revolutionary Electrochemical Thermal Converter (ETC) which operates at low temperatures (under 100°C) and converts through an electrochemical process the thermal energy into electricity with a high efficiency (up to 75% at 98°C input temperatures). Most of the resulting DC electricity is converted into AC current and sent to the user / or the grid and part of it is used to charge the proprietary Flow Battery, or to supply electricity (if the case) for the proprietary Hydrogen Electrolyzer and reactor and for plant’s operating components (pumps, lighting, etc.).
4. In case of large plants hydrogen could be used as energy storage agent, based on a proprietary Hydrogen Storage Technology. Part of the DC current generated in this case would be used to produce hydrogen in a high efficiency electrolyzer. The hydrogen is then attached in a proprietary reactor to a support substance at normal temperature and pressure and extracted afterwards as needed and combusted in a compact reactor as an alternative heat source for the plant, or it could be sold to outside users.
Proprietary Technologies to be used in the Lion Solar Thermal Plants
The Electrochemical Thermal Converter
The Lion Electrochemical Thermal Converter (ETC), the central piece of the Lion solar plants, is a revolutionary technology for the direct conversion of low temperature heat into electricity based on a continuous regeneration of an electrolyte using the thermal energy of a heat source. The thermal/electrical energy conversion efficiency is 65% – 75% (75°C at 100°C input temperature), surpassing the limitations of the Carnot cycle. (considered theoretical limit of most efficient cycles for the conversion of thermal energy into work).
The Converter has been tested at the lab level. The first generation prototype has a specific power production density of approx. 30 KW per m3 of installation volume. The next R & D stage will include scaling up the prototype and pursuing the electronics & automation components with the focus on increasing the equipment power density. The cost of the converter is estimated to represent 30% of a gas turbine’s cost (the lowest specific cost among existing fossil fuel based energy technologies). The simplicity of the system, low maintenance cost and long economical life will have a further impact on the levelized energy costs.
The converter does not have any moving parts, the economic life is estimated to at least 20 years and the modular structure allows for easy low cost replacement of components. The materials used are readily available and non toxic, most are recyclable, and the equipment production and assembly plants require low capital investments and could be deployed in short periods of time.
The Use of the Converter in Residual Heat Recovery
The ETC was developed initially as an intended component of the Lion solar power plants but due to its high efficiency, low cost and the ability to work with low input temperature, it actually has a vast range of potential applications as a substitute for existing Rankin cycle turbines applications.
In spite of unprecedented societal technology advances, the electricity production efficiency has been frozen in the last 6 decades. The average generation plant converts 36% of the input energy into electricity and after transmission losses only approx. 33% of the energy in the fuel reaches the user. Energy losses increase with the exhaust temperature and at greater than 900°C they represent at least half of the total fuel input to the process.
Existing low cost power plants operate near capacity and new generation construction will require in addition to capital to build the plant and emissions abatement equipment up to $1,400/Kw in capital for new transmission & distribution (T&D) infrastructure. Recycling Waste Energy is the obvious available solution to increase electricity generating capacities by up to 50% at a reduced capital cost, avoiding the construction of new plants (requiring hard to approve sites) and new T&D infrastructure and reduce pollution and water usage. But based on existing technologies, the recovery of the under 300°C waste heat is thermodynamically limited and the economic benefits do not justify the costs involved in every application. Possible uses are limited to preheating combustion air, space heating, pre-heating boiler feed water or process water.
Existing technologies for the waste heat recycling include Steam Rankine Cycles (for high temperatures) and Organic Rankine Cycle – ORC (for medium to high temperatures). ORC cycles have been around since early 80’s (Kalina cycle) using as heat transfer fluids ammonia, freon, water, propane, iso-pentane, iso-butane, etc. Emerging technologies include Supercritical CO2 or Brayton Cycle (not in commercial stages yet).
Combined Heat & Recovery plants (CHP) are becoming popular with clean energy proponents, but the operators in this field have to cope within the limitations of existing technologies since the energy content of the waste heat must be high enough to operate the equipment found in cogeneration and trigeneration power systems.
The low cost Lion Electrochemical Thermal Converter has a high efficiency (70 – 75%) and can operate at low temperatures (down to 70°C) so it can be used to convert to electrical power the trillions of BTU’s in waste heat available from fossil fuel power plants and industry lost every year. Due to the polymer conduits the system will not be affected by the scaling and corrosion caused by dirty wastes found often in the low heat agents.
The Use of the Converter in Geothermal Applications
A fascinating application of the Lion ETC is foreseen in the capture of the ground heat. The geothermal resources occur in various forms: hydrothermal (water or steam), low temperature aquifers, normal gradient (the heat flow from the earth’s crust to the surface) and hot dry rock (largest resource but typically at considerable depth). Until recently, existing geothermal power applications have been able to harvest only geothermal resources in places where local geology brings hot water and steam near the surface.
There is though a large quantity of untapped heat generated deep within the earth by the decay of naturally occurring isotopes. The developing Enhanced Geothermal Systems (EGS) technology is proposing to capture this heat by drilling holes up to 5,000 m deep and circulating water through fractured granite which is hot due to radioactive decay of trace elements. The estimates for such heat for the whole planet are 100 million exojoules or quads (1 quad = one quadrillion BTUs). Since the current energy use worldwide is just over 400 exojoules per year, the world energy consumption could be covered by capturing just a fraction of this available heat.
Commercial EGS projects are under development or operational in Australia, UK, US, Germany, France. Cooper Basin project in Australia has the potential to generate 5,000–10,000 MW. The use of supercritical CO2, instead of water is examined as alternative working fluid, with benefits in carbon sequestration and water use.
The low operating temperature Lion technology could be used to capture the vast available geo – heat, and
provide low cost power on demand, using the ideal storage of the earth’s hot interior as reservoir. This could provide peak load, intermediate or base load electricity.
Hydrogen Based Energy Storage
Lion has developed a technology for the long term storage of energy using hydrogen as storage agent. The technology consists of the catalytic hydrogenation of a support substance in a proprietary reactor. The process has been fully researched and experimented at industrial scale and is ready for applications.
The hydrogenated support substance can be stored at normal temperature and pressure and is extremely stable, with energy density of approx. 2,245 Mwh / m3 of support substance.
A hydrogenation reactor with a volume of 1m3 can generate a flow of approx. 780 Nm3/h (2.77 Mwh energy content). The cost estimate of the equipment produced in Eastern Europe (not including the support substance storage tank) is under USD 100/Kw (caloric energy released by combusting the hydrogen for 1 hour).
By comparison, the energy density of liquefied hydrogen, (highest energy density storage for hydrogen), is approx. 2,33 Mwh /m3, but the production and the transportation of liquefied hydrogen is costly and generates high energy losses. In theory, large size liquefaction plants (10,000 kg H2/h, or four times larger than any existing facilities) would consume at least 40% of the HHV energy (intrinsic energy content of hydrogen) to liquefy hydrogen. But in reality, for small existing plants, the energy needed to liquefy hydrogen could possibly exceed the resulting HHV energy. Liquid hydrogen may also loose some 3 – 4 % gas per day by boil-off.
Transporting hydrogen in the form of gas using the existing natural gas pipes infrastructure is not feasible, due to the leakage and the hydrogen causing the existing pipes to become brittle, so hydrogen has to be transported currently in special tanks under pressure, with all costs and losses related disadvantages.
In case of the Lion technology, the support substance (together with the hydrogen and the energy contained) could be stored indefinitely or transported using methods and equipment similar with the infrastructure created by the oil industry.
The Lion Polymer Solar Thermal Collectors
The Lion solar thermal collectors have a proprietary modified hybrid flat plate design with low cost and high thermal efficiency. They are made out of resistant polymers 100% recyclable with stability to photo and thermal degradation. They have a proprietary design reducing energy losses from convection and are using selective surface coatings that are good absorbers of short-wavelength solar radiance but poor emitters of long-wavelength (infrared) radiant energy. Lion has experimented with a lab prototype and continues testing with new coating materials which would absorb efficiently a larger spectrum of wavelengths of light from a wide range of angles.
The Lion collectors absorb both beam solar irradiance and diffuse irradiance (which predominates on cloudy days). That is why in moderate climates locations tracking equipment is optional, due to their ability to collect the diffuse component of solar irradiance coming from all directions. This could offset part of the beam irradiance lost in installations where the collectors are set at a fixed tilt angle (equal to the site latitude) with the advantage that rigid connecting plumbing may be used in this case.
In high desert climates fixed flat-plate collectors lose more energy from the cosine effect (reduction of solar irradiance by the cosine of the angle between the surface and sun rays) than they gain by being able to collect diffuse energy and in that case the low cost of the collectors makes economically feasible the increase of the collector active surface by 20 – 30%, as a compensating alternative to high maintenance sun tracking devices.
The Lion collectors cost 5 – 10 times less (under USD 3/sf) than existing thermal collectors and their cost represents only approx. 10% of the total capital cost of the solar plants while in the case of other solar thermal technologies collectors are the major capital cost.
Due to the low cost collectors the Lion solar power plants can provide continuous electricity production at a minor cost increase by adding additional collectors required for the generation of the energy to be stored. Where land cost is a factor, one direction tracking devices could be used.
The low operating temperature of the Lion collectors (70°C – 100°C) confers them functional, cost and energy loss reduction advantages not available in case of the existing solar thermal technologies operating at high temperatures (300°C – 700°C). The collectors have a thermal efficiency of 75 – 80% due to their proprietary design and the low operating temperature and a specific weight of approx. 25 Kg/m2.
The polymer collectors and fluid conduits are low maintenance and easy to replace. In case of existing CSP technologies (trough, Fresnel or tower) the high heat and pressure at which the transfer fluid operates require special materials and high cost equipment. The 4% annual brake rate of reflectors and receiver tubes and reflectors’ cleaning requirements lead to increased operating costs.
The simplest, least expensive type of solar collectors which could work in conjunction with the Lion electrochemical thermal converters could actually be shallow solar ponds consisting of plastic liners lying on top of insulation laid on graded ground. They could be practical only where site economy is not a priority since the lower operating temperature of the pond water would reduce system’s efficiency and require a larger site.
Lion has developed a low cost thermal storage technology based on proprietary solutions and components which reduce thermal losses through convection and radiation, using water as storage medium and hollow tubing (proprietary Lion product) for the fluid circulation, layers separation and for heat exchanging.
In case of thermal storage the energy is lost through conduction, convection and radiation.
The thermal storage tanks in general generate through convection entropy and destroy exergy (the energy component which can be transformed in work). The reduction of heat losses by convection is realized in the Lion tanks by creating constructive compartments using hollow tubing which prevent the uncontrolled movement and mixture of fluid layers with different temperatures.
The thermal loss by radiation is the highest of the three energy loss venues (the radiation of a warm body increases by the 4th degree of its absolute temperature – Stefan &Boltzmann) and the most difficult to control. The range of losses is over 30% in case of low and medium temperatures and it could equal in some high temperature circumstances the value of the entire heat energy collected from the sun. The thermal losses by radiation is reduced with radiation screens which reflect back towards the warm interior of the tank a part of the radiation which is then reabsorbed by the radiating material (Kirchoff).
To reduce losses through conduction the thermal storage tank is surrounded with insulation materials with low thermal conductivity (k).
The fact that the entire Lion system operates at temperatures below 100°C represents a major advantage in increasing the feasibility of the thermal storage reducing the losses by radiation. The other existing CSP thermal technologies operate in high heat and pressure environments (300°C – 600°C) and pressure (30 – 100bar) and have to use for the storage and thermal exchange high cost materials. Even in case of systems storage based on latent heat the melting temperature of the phase change materials used is in the range of 230°C – 330°C.
For applications storing energy for more than 10 hours operation or requiring economy of space Lion is working on a sorptive system concept (with a moderately higher cost) which can increase the thermal storage density up to 4 times. In this case an adsorbent material can bind a high amount of water and release it at a later time when needed without thermal energy losses.
The Lion Proprietary Hollow Tubing
The Lion proprietary hollow tubing offer an outstanding ratio stress resistance / specific weight, which lends it to usage in a large range of applications.
The hollow tubes could be manufactured in a large assortment with various mechanical resistance, porosity, resistance to heat and light exposure or acids depending on:
Lion applications using hollow tubing include solar thermal collectors, thermal storage, heat exchange, versatile construction materials, subsurface irrigations (with major water, energy and equipment cost savings).
The Lion technology will allow the production of electricity in fully dispatchable solar thermal power plants at costs below the cost of electricity generated by PV solar or fossil fuel plants.
Based on its ability to operate at low temperatures the Lion technology will also allow the capture of the waste heat available from fossil fuel power plants and industry and also of the huge reserves of untapped low temperature high depth geothermal energy.