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ISIS Report 10/12/08

Portable and Distributed Power Generation from LENRs

Power output of LENR-based systems could be scaled up to address many different commercial applications  

Lewis Larsen

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Total output of LENR-based power generation systems highly scalable

Low Energy Nuclear Reactions (LENRs) have a unique ability to generate enormous amounts of nuclear heat from specific types of very small surface hot spots up to tens of microns in diameter [1]. By controlling the distribution of sizes, initial composition, and area-density of nanomaterials that support the formation of such hot spots, LENRs could be scaled up in terms of total heat output. 

In principle, LENR heat sources could be designed and engineered to create any desired power output and/or system working temperature, short of melting key structural components that maintain the system’s physical integrity, or otherwise overloading its thermal management capabilities. They could provide a clean, green source of carbon-free energy for use in a multitude of important commercial applications.

Potential energy yield from LENR fuels several thousand times larger than burning gasoline

The calculation of energy yield for a prospective LENR target fuel is straightforward. It involves two steps: (1) deciding which ‘base fuel’ (hydrogen or deuterium) to use for producing LENR neutrons that can then react with a prospective target fuel, this choice determining the energy ‘cost’ of the necessary neutrons; and (2) calculating the nuclear energy released by a particular target fuel when it subsequently absorbs (captures) the neutron(s).

 It 'costs' a minimum of 0.78 MeV of input energy to make a heavy-mass electron (e*) that has enough additional effective mass-energy to successfully react with a given 'base fuel' such as hydrogen H = (p) or deuterium D = (p,n) to produce the ultra low momentum (ULM) neutrons (n). The required input energy that is ‘pumped’ into the collective plasmon polariton electrons found on all metallic hydride surfaces can be in the form of an externally imposed electric current, laser pulse, injection of energy into a local magnetic field, pressure gradient across a metallic hydride ‘membrane’, and so on.

The minimum input energy ‘cost’ to make a heavy electron (e*), is exactly the same, 0.78 MeV, regardless of whether H or D is used. While D is a much more expensive ‘base fuel’ than is ordinary hydrogen, it is still an attractive option for many commercial LENR applications because it produces two LENR ULM neutrons for the input energy ‘cost’ of one [2], so the cost per ULM neutron is just 0.39 MeV for D instead of 0.78 MeV for H.

If, upon absorption of neutron(s) by a given target fuel atom, subsequent reactions release somewhat more (losses to neutrinos must be factored in) than 0.78 MeV (using H) or 0.39 MeV (using D) per neutron absorbed, then the LENR fuel burn-up process exceeds breakeven; i.e., you are then ahead of the game, at least as far as the overall energetics is concerned.

The energy range of individual beta decays extends from keVs up to ~20 MeV for certain neutron-rich isotopes [3]; many potential LENR target fuel beta decay processes are well-above the breakeven point. The multi-step LENR reaction series outlined in our 2006 paper [2] (see LENRs for Nuclear Waste Disposal [4], SiS 41) actually has one step that involves the perfectly symmetric fission of a very light nucleus, beryllium-8 (half-life 10-18 second) into two helium-4 atoms without producing any high-energy gamma or neutron emissions. That particular LENR reaction series starting with lithium-6 releases a total energy of ~ 27 MeV, which is roughly comparable to the amount of energy released by nuclear fusion reactions. By itself, the lithium-8 beta decay step releases ~ 16 MeV [2]. While such energy releases are several thousand times more powerful than 100 percent efficient chemical combustion of gasoline, they are nonetheless green, as they do not produce carbon dioxide, long-lived highly radioactive products, or ‘hard’ gamma and/or X-ray photon radiation.

Widom-Larsen theory successfully predicts experimentally measured LENR rates

In numerous experiments involving well-performing Pons-Fleishmann-type electrolytic cells (with either light or heavy water) [5] (see From Cold Fusion to Condensed Matter Nuclear Science, SiS 36), LENR production rates on the order of 1 x 1011 to as high as 1 x 1016/second have been measured with reasonable precision. These values for reaction rates hold true whether the LENR transmutation products are in the form of helium-4, or the complex arrays of different-mass isotopic products such as those found in the experiments of Miley and Mizuno [6-9].

Most cathodes in such experiments had working surface areas of roughly a centimeter or two; nearly all of them had significant amounts of lithium present in the electrolyte. According to the Widom-Larsen theory, neutrons are required to trigger the subsequent nuclear reactions capable of producing such transmutation products; therefore ULM neutron production rates had to be greater than or at least equal to the observed LENR product production rates in those experimental systems.

Importantly, we performed a difficult first principles theoretical calculation of predicted LENR ULM neutron production rates [1] for (effectively) a cathode in an electrolytic cell. We predicted neutron production rates of the order of 1012 to 1014/cm2/second; these calculated rates matched the best available experimental LENR rates.

Hypothetical energy releases from a small LENR device using a lithium-6 reaction

To illustrate the tremendous commercial potential of LENRs for use in small, battery-like portable power generation systems (see below), we shall examine the maximum amount of energy that can be obtained from an idealized system.

To simplify our calculations, we assume that conversion of input energy (in this case, an electric current) into energy available to produce LENR ULM neutrons is 100 percent efficient in order to estimate a theoretical upper bound on potential energy releases from a small LENR heat source.

We will also assume that 100 percent of the ULM neutrons produced in the hypothetical device are absorbed locally (a pretty safe bet that is supported by 19 years of experiments) and that they are only absorbed by a ‘target fuel’ comprising isotopically pure lithium-6, resulting in a series of nuclear reactions beginning with lithium-6 and ending with helium-4 [2]:

Lithium-6 + 2 neutrons à 2 Helium-4 + beta particle (e) + neutrino (n)  + 26.9 MeV (1)

The details of which are:

Li-6 + n à Li-7 + n à Li-8 à Be-8 + e+ n   {neutron absorption, then beta decay} (2)

Be-8 à He-4 + He-4 {perfectly symmetric, ‘green’ fission of a Beryllium-8 nucleus} (3)  

Lastly, we will assume that the ‘base fuel’ used to produce LENR ULM neutrons in our hypothetical device is deuterium and that it has an LENR-active working surface area of 1 cm2.

The input energy required to produce 1 neutron/cm2/sec from deuterium ‘base fuel’ to react with the lithium-6 ‘target fuel’ is 0.39 MeV per neutron. However, according to Eq. 1, we need two ULM neutron to complete the entire series of reactions, so the required total input energy to the device is 0.78 MeV/cm2/sec.The net energy release from that particular series of LENR reactions starting with lithium-6 is 26.9 MeV/cm2/sec = 4.28 x 10-12 J/cm2/sec (1 eV = 1.602 x 10-19 J). The 26.9 MeV represents a theoretical upper bound of ~ 34x total input power.

As there are ~ 1014 of these 26.9 MeV energy releases taking place per second on the 1 cm2 LENR device, the total energy release is 4.28 x 10-12 J/cm2/sec x 1014 = 428 J /cm2/sec. This represents 428 W/cm2, a large power density. At a lesser ULM neutron production rate of 1 x 1012/cm2/sec, the overall energy production rate would drop down to 4.28 J/cm2/sec or 4.28 W/cm2. At a ULM neutron production rate of 1 x 1011/cm2/sec, the energy production rate would drop down to 0.428 J/cm2/sec or 0.428 W/cm2, which is close to levels of excess heat output that are often observed in the limited subset of electrolytic LENR experiments that researchers deem ‘successful’ at making heat. According to our theory, experimentally observed ‘excess heat’ from LENR devices should be closely correlated to their rates of ULM neutron production.   

In this example, an energy generating rate of 428W/cm2 means 0.428 kWh/ cm2 produced in an hour for a lithium-6-fueled 1 cm2 LENR device, without releasing any CO2. In comparison to the minuscule total mass of LENR reactants, the complete combustion of 1 US gallon of gasoline (weighing 2.7 kg) generates ~33.56 kWh of heat energy and releases ~8.8 kg of CO2 into the atmosphere.   

Scaling up the surface area of the idealized LENR device 1 000 fold would give a 428 kW power source, while a 1 m2 device would give a 4.28 MW power source.

Experimental LENRs to-date very suboptimal with regard to energy output

Up to now, and depending on the specific type of experimental system involved, in the limited number of LENR experiments in which significant amounts of excess heat production have been reliably observed, power output is generally well below 1 W on average. In an even smaller number of successful experiments in which researchers sporadically manage to produce 1–2 Watts or more of excess heat over a period of hours or days, there were probably still only a relatively small number of  surface ‘patches’ that are LENR-active and producing ULM neutrons at any given time. Those tiny surface regions are the so-called ‘hot spots’, the effects of which can be seen in post-experiment SEM images of the surfaces on LENR devices [10], or the ‘fireflies’ seen in high-speed infrared imaging during cathode operation [11].

Interestingly, back in the 1990s some talented researchers at the University of Sienna in Italy produced nearly 20 Watts of heat for almost a year using a gas-phase nickel electrode hydrogen system [12]. They were able to repeat it several times in a hit-or-miss fashion but unfortunately didn’t understand the underlying physics and fabrication issues well enough to be able to readily reproduce their spectacular results.

LENR heat sources could be integrated with various energy conversion technologies

A major difference between chemical batteries and Lattice’s proprietary LENR power generation technologies is that with batteries the on-demand conversion from stored chemical energy into electrical power output is automatic and ‘built in.’ In the case of LENR-based power generation systems, nuclear reactions are used to produce raw heat, which must then be converted into usable power by separate, integrated energy conversion subsystems. For example, in an integrated LENR-based portable power generation system, solid-state thermoelectric devices [13-15] could be used to convert raw heat directly into high quality DC electrical power.

There are many different kinds of off-the-shelf energy conversion technologies that could be integrated with high performance LENR-based heat sources for particular application requirements, performance, and power output. These involve various types of heat-to-electricity conversion, heat-to-shaft-rotation, heating of working fluids, and so on.

Available types of energy conversion subsystems that can be used in different configurations with LENRs include thermoelectrics or thermionics (the production of electric power from heat using vaporized electrons from a hot electrode) [16]; Stirling engines (in which work is done by the expansion of a gas at high temperature) [17]; or steam engines [18], turbines [19]; microturbines [20-21]; boilers [22] and steam plants. Other possibilities are optoelectric nuclear battery configurations [23] (in which beta-emitters are used to excite light emitting gases to generate electricity in a photovoltaic layer); beta voltaic nuclear battery configurations [24] (in which radioactive sources emitting beta particles are used to generate electricity directly); and other direct energy conversion technologies [25, 26] still under development.

Many commercial applications for future LENR-based power generation systems

In principle, total energy output of fully integrated LENR-based power generation systems could be scaled-up to any value within reason. This would enable many different types of cost-effective commercial systems with power outputs ranging from microwatts to megawatts. Applications for such systems could include: portable power generation; stationary distributed power generation; propulsion for transportation; and eventually, large-scale many-megawatt grid connected power plants.

Over time, LENRs may have the potential to gradually replace internal combustion engines now used in ground transportation with carbon-free, all-electric or steam propulsion systems. Megawatt-output LENR-based propulsion systems could also be used to power long range manned aircraft [27] and various types of unmanned aerial vehicles (UAVs) [28]. Aircraft equipped with such systems might be able to circle the earth without refueling or emitting carbon-rich exhaust gases into the atmosphere. With LENR-based aircraft propulsion, there would be no risk of releases of radioactivity or radiation in the event of a crash; neither would there be any need for heavy shielding to protect passengers, crew, or vital electronics.      

Unlike uranium, fuels for LENR-based power generation systems are non-radioactive, comparatively inexpensive, and relatively abundant   

Fuels for different versions of Lattice’s planned commercial LENR-based portable and distributed power generation systems include protons or deuterons, electrons, and a variety of different types of stable target fuel atoms/isotopes that can be used to release nuclear binding energy (e.g., lithium, nickel, titanium, etc.). Protons and deuterons are ‘base’ LENR fuels found in water and hydrogen gas; and there is no possible future shortage; free electrons are found on the surfaces of all metals; so no potential shortage there either.

Readily recoverable global reserves of some LENR target fuels include: lithium, ~28 million tons [29]; nickel, ~23 billion tons [30]; and titanium, ~600 million tons [31]. These are much more abundant than the world’s estimated uranium reserves of ~5.5 million tons [32 - 34], from which U-235 is enriched to make the nuclear fuels that are now used in almost all commercial fission power plants (see also [35] The Nuclear Black Hole, SiS 40)

World reserves of potential LENR target fuels are also more abundant than thorium [36] (estimated reserves are 3x uranium). Fertile thorium-232 provides the basis for an alternative type of nuclear fuel cycle involving fission of uranium-233 [37] rather than U-235; it is still in the R&D phase, with India and France particularly active.

The author declares his commercial interest as President and CEO of Lattice Energy LLC.

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