Report 2 – Strategies for Materials that Save Energy and Cost

Report 2 – Strategies for Materials that Save Energy and Cost

By: Armando Moncada, Certified Energy Manager

(Please Note: The United States Patent Office prohibits patenting work that is already part of published material. If it is not your work you cannot patent it. These reports are brief white papers not patent ideas. They are part of the public domain.

Secondly, these ideas are being shared in an open-source manner with everyone including designers, manufacturers and researchers to discover effective means of reducing energy costs. We encourage individuals, facility owners, businesses and research centers to explore the ideas and develop them even further. This idea pool is available to the public to directly address energy efficiency within product design, in an effort to globally update our technology, reduce CO2 emissions and reduce energy consumption. Good luck, be safe and have fun!)

The focus of this report is on material strategies that facilitate energy and cost savings. The way we use materials may affect weight, susceptibility to corrosion, thermal conductivity, compactness and net volume, insulation values, CO2 emissions and financial planning. The perception of accessibility to materials also affects our willingness to think of certain materials as favorable or cost prohibitive. Material topics were selected that directly define how mechanical equipment might consume energy, or how components in a building might be manufactured and maintained. Each topic will be described below in a list form; ten topics were selected.

 

1.      Helium as an Additive to Refrigerants

Refrigerants vary significantly in their properties. Some refrigerants have a very high degree of thermal conductivity, while others are average. In addition, each refrigerant varies in its thermal conductivity depending on temperature, pressure and phase. For example, Helium is 5.82 times more conductive than Air. Below in Table 1 is a list of conductivity values at 1 atmosphere of pressure.

In 2025, two new refrigerants presented themselves on the market: R-32 and R-454B. HVAC Engineers are being advised to switch from older refrigerants to newer ones to meet new Global-Greenhouse-Gas Warming Potential regulations, (GWP). With a baseline value of 1, CO2 is the reference for other refrigerants. 700 is considered the maximum GWP value that is recommended. New refrigerants comply with this limit, see Table 1 below. Helium has a global warming potential value of 0.

Table 1. Comparison of Refrigerant Properties:

Refrigerant	Relative Cost	W/m-K at 1 Atm (Gaseous)	Boiling Point	GWP
CO2	Low but varies significantly	0.017	-78.5 C	1
Air	Free	0.026	N/A	0
He	Higher by a factor of 10X but will be used only as an additive by 15% to 20%	0.1513	-268.9 C	0
R-32	Average range	0.0124	-51.7 C	675
R-454B	Average range	0.013	-50.9 C	466

Phase associated conductivity can also vary significantly, in the liquid state, for example R-32 is 0.135 W/m-K and in the gas state it is only 0.0124 W/m-K.

The thermal conductivity of Helium is impressively high at 0.1513 W/m-K, plain air for example is 0.0260 W/m-K. Helium is 5.826 times more conductive than Air at operating temperatures.

Helium can be added to compressed air systems in a fractional ratio of 15% to 30% to achieve a filling of void space which mimics the conductivity of Helium alone. Testing will verify the conductivity of Helium/Air mixes at various ratios. For example, it would not be a surprise if adding 10% helium to air to improve conductivity increases the conductivity by more than 20%, because the helium and the air molecules work together to fill the void space. In summary, the relationship between mix percentage vs. thermal conductivity is most likely non-linear and in favor of energy savings.

Cost remains relatively high for Helium, it is priced significantly higher than other refrigerants, but one doesn’t have to fill the entire volume of the heat exchanger coils with Helium, only 15 to 20% as a preliminary estimate.

Small atom considerations - if helium is the second smallest atom, containment within metal coils at a high pressure may be an issue. If so, aluminum might serve as a better coil material than copper for the simple reason that aluminum forms a hard ceramic oxide layer on its surface. Treating aluminum at a high temperature, in an oxygen-only kiln might thicken this layer, enabling capture to occur more easily.

Secondly, because helium is a lightweight gas, the low inertia of the gas on the compressor will likely improve its operating efficiency significantly, meaning it is easier to move through a system. A helium/air mix where 30% helium is added would reduce the overall average molecular weight of the gas and the density to 78% of the original weight of the gas. Energy savings are predictable. Improved efficiency may be enough to justify seasonal Helium repurchasing, so long as the escape rate is very low and acceptable, if it even exists at all.

Helium as a more conductive gas also shortens HVAC start up times, coils can reach their target temperature in less time.

Lastly, helium is being added to a system that can already function using only compressed air or other more typical refrigerants, it just improves efficiency.

Final point – expansion valves may require redesign to create a tighter seal for such a small atom.

 

2.      Graphite as an Additive to Sand in Thermal Energy Storage Systems

Thermal Energy Storage Systems that use sand as the conductive medium can benefit greatly from the addition of graphite. Graphite has a thermal conductivity of 200 – 500 W/m-K while course dry sand achieves only 0.25 W/m-K and moist fine grain sand can achieve values as high as 1.7 W/m-K. The void spacing in a sand bank defines the minimum percentage of graphite that should be mixed with fine grain sand. Void spacing can be measured easily by volume by adding water to a mL marked glass of sand and then removing the sand, comparing the two volumes yields the volume of void space per volume of sand. Courser sand can also be used but has a larger void space, which is unnecessary and costly, since graphite powder is more expensive as a material.

 

3.      Method for Graphitization of Carbon with Coke as the Source

The process of transitioning carbon into graphite is known as graphitization. Carbon has a sublimation temperature which is close to 3550 C. There is a stark difference between carbon in the form of coke and graphite. Graphite is made of carbon, but the elevated conduction properties of graphite are based on molecular bonding formed during a process similar to the annealing of metals. By sufficiently heating the carbon-coke to elevated temperatures, the heating energy changes the bonds to a more organized bonding structure. This in turn removes grain boundaries that are randomly oriented, and the carbon mix becomes like a unified crystal; a common crystal lattice is formed that enables extremely high thermal and electrical conductivity.

A method for making graphite synthetically can be elaborated such that carbon in the form of coke is graphitized in a kiln with lasers directly overhead. With renewable energy as the energy source, major energy costs can be avoided. Annealing temperatures for graphitization range from 2200 C to 3000 C. Different authors report different temperatures to achieve the process. Inert gas is also required to avoid oxidation. Argon is the most abundant inert gas.

During graphitization, power input (kW) is proportional to the required heat to sustain the kiln temperature plus the required power to graphitize the carbon. The power input can be greatly reduced via extreme insulation. The power input can also be reduced significantly by employing hydrogen. This process is described below.

 

 

4.      Graphitization via Using PET Plastic for the Carbon Source, Hydrogen Combustion for the Heat Source and an Air-to-Air Heat Exchanger

Carbon sources are numerous but single use plastic bottles represent an opportunity for pure carbon acquisition. In the polyethylene terephthalate molecule, (PET), the hydrogen to oxygen ratio is 2 to 1. PET has a molecular formula of C10H8O4. Water or H20, the product of hydrogen combustion, also has the same ratio. Hydrogen burns at 2800 Celsius in a pure oxygen environment, and we established earlier that graphitization occurs between 2200 and 3000 Celsius depending on the method used. The only question remaining is how can we use focused laser light which can break up molecular bonds in PET plastic materials without hydrogen combustion occurring? The answer is simple – vacuum pumps are employed to create a low-pressure anaerobic environment, pulling away all gases before they can combust. The vacuum also assists in breaking the Carbon-Hydrogen Bond as reduced pressure pulls on the gas.

By using the hydrogen-oxygen gas mix on demand, without storing rather redirecting it to a second kiln; carbon acquired can be heated to required temperatures.

Rule of thumb: always avoid storing oxygen and hydrogen in the same container. It is very dangerous to do so, since less than 100 micro-Joules will initiate the combustion process.

There are many sources of energy and many sources of carbon, but this is one example. This process recycles hydrogen into an energy source and procures carbon in way that prevents non-degradable additions to landfills.

Obtaining the carbon and hydrogen-oxygen mix should be treated as a separate step to avoid creating a vacuum with high temperatures.  

The final step is designing the graphitization kiln via a cost-effective means. This method would involve creating a kiln out of graphite and burning hydrogen and oxygen in an air-to-air heat exchanger which would simply be a channel system formed within the walls of the graphite kiln. It would be relevant to avoid mixing carbon with oxygen at elevated temperatures because carbon dioxide will form. This kiln would operate at 1 atmosphere of pressure and would best be employed by creating hydrogen on demand and recycling the water that condenses after combustion. The tunnels should be equipped with an additional layer of piping conducive to blocking CO2 formation in extremely high temperature environments. Graphite tubing can be employed. Lastly, hydrogen could be formed through high volume formation via electrolysis if the supply from the PET laser process is insufficient, which is why it is effective to have the option to recycle the water in the design of the piping system.

 

5.      High Temperature Kiln Wall Design with Refractory Bricks and Laser Sintered Metal Structure

Kilns can be designed in numerous ways. By using ceramic and metal powders suitable for high temperatures and select laser sintering - CNC machines, we can realize the ability to manufacture kilns at a low cost. Certain ceramics also lend themselves to liquid casting such as Magnesium Oxide.

If tungsten powder is employed, an anaerobic environment must also be maintained once the temperatures are elevated, otherwise rapid oxidation will occur. Secondly, instead of refractory bricks, ceramic bricks can be made via liquid casting Magnesium Oxide, with air gaps, which has a melting temperature of 2852° C. Another option is laser sintering Silicon Carbide, which melts at 2730° C. Tungsten’s melting temperature is much higher at 3,422° C. Calcium Oxide can also be laser sintered and works well for capturing CO2.

When magnesium oxide is cast from a slurry, the process is very similar to concrete casting but is slightly exothermic. The mix may border on feeling uncomfortably hot, but not to the point of burning the user. Sand and other filler materials can be added if the mold walls are thick enough. Lastly, other materials can be added to form the air gaps in the first place instead of designing a mold with many parallel laminates. One option might be to design a brick-like shape and add Styrofoam pellets or wax pellets. Proper ventilation will be required when the kiln bricks are used the first time.

Figure 1a – Example of a Cylindrical Kiln with Laser Sintered Tungsten Acting as the Exterior Structure with a Crosshatch Air Gap Insulation Pattern. 

Figure 1b – Ceramic – Metal Interface. Tighter Air Gap Spacings Face the Center of the Kiln

 Tungsten has a very high melting point, at 3,422° C, and can withstand heat very well. Because the furnace temperature may pass the creep temperature, additional support must be added to prevent the tungsten from deforming at higher temperatures. Especially if very thin layers are part of the design. In Figure 1b, this problem is solved by allowing the tungsten to act as the structure and laser sintering Calcium Oxide for the refractory Bricks to act as an intermediate insulator layer. Calcium Oxide melts at 2613° C.

Tungsten oxidizes at high temperatures very easily so the kiln should be protected by an inert gas environment.

This method of vacuum panel manufacturing allows one to discover the benefits of using vacuum panels which have a relatively high R-Value and can be manufactured with Select Laser Sintering Machines. One should avoid mixing vacuum panels with temperatures that climb higher than 40% of the melting point of the material. Under high pressure, it is very predictable that materials will deform.

  

6.      Graphite + Plastic as a Suitable Substitute for Copper in Low Temperature Heat Exchange Processes

There are many pieces of equipment that are used in building components that function as low temperature heat exchangers operating at atmospheric pressure. An example may be a fan coil unit in the ceiling, an air handling unit in a mechanical or an energy recovery unit at the exhaust air-outside air interface. For applications such as these, mixing plastic with graphite and cast molding heat exchanger coils becomes a very relevant option for manufacturers seeking to create coils with a higher degree of thermal conductivity, a lighter weight, an easier manufacturing process and a lower cost. This strategy is dependent on the market costs of the graphite powder, but a manufacturing process like this is still feasible since manufacturing coils out of copper is more labor intensive. This may also apply to thermal energy storage systems, (the cold side), radiative cooling panels, solar thermal heating systems, and refrigerators.

Plastics worth recommending include polycarbonate and acrylic. Polycarbonate will degrade in the sunlight, and both will absorb less than 0.4% by weight when exposed to wet environments. Connections should be designed to be flexible to compensate for different expansion rates and water absorption rates when interfacing with other materials. The percentage of graphite to be added should remain high enough to increase thermal conductivity to desired levels and low enough to avoid compromising the structural requirements. Graphite will also remain a powder embedded in the plastic, so its structural strength can be calculated as zero. Low percentage of graphite ensure that the plastic fully surrounds the graphite. Do not exceed 20%. Patterns or pathways can also be employed where graphite and acrylic are mixed in different percentages at different points in a part to allow for increased thermal conductivity in certain areas, preserving structural strength in other areas of the part.  This is done to reduce the net cost of the graphite per part and preserve material strength. Automation can be employed to reduce labor costs. Injecting plastic into a mold a second time is sufficient to form a bond between the two parts, but seam lines will not have the same strength, so parts should always be tested.

 

7.      Glass Cabling for Additional Strength of High-Pressure Plastic Tubing with Graphite

Some types of plastic applications require piping to operate under high pressures and temperatures. Acrylic, for example, has a glass transition temperature of 85 Celsius, so under pressure it will deform because of high temperature exposure, but if the temperature is well below the glass transition temperature, glass fibers can be added for additional strength, enabling plastics to operate in high pressure environments without failing. This is a common solution for high pressure plastic piping but can also be employed in plastics mixed with graphite for added strength, since the graphite mix reduces the overall strength of the plastic.

 

8.      Vacuum Panels with Pressures below 0.01 Atmosphere

Vacuum panels can be employed for applications with higher R-value requirements. For example, a thermal energy storage system works well with flat vacuum panels. The vacuum forms a void space which blocks two types of heat transfer from occurring in the void space, conduction and convection. The only major conductive bridges that remain are at the edges and through the structural bars. However, the cross-sectional area at the middle of the support bars has significantly been reduced via the design of the structure.

Figure 2a – Vacuum Panel with Internal Structural Support

As panels are manufactured at a larger scale, the ratio of area to perimeter increases, raising the net R-Value. If the panels were applied cylindrically, it would increase even more, since one can do away with most of the perimeter. In the case of a sphere, although significantly more challenging, the perimeter does not exist.

In Figure 2b, a ceramic with a very high compressive strength is employed at the center of the structural bridge, to minimize the cross-sectional area. The ceramic insert should be of equal diameter along its height to avoid stress concentration.

Figure 2b - Vacuum Panel Structural Support Detail

 

9.      Redirecting Radiation with Perforated Concentric Kiln Wall Laminates + Reflective and Absorptive Surface Coatings

Perforated kiln walls can be created that redirect radiation to the center without diminishing the net insulation value. In physics there is a famous experiment called the double slit experiment, where light arrives at a wall, passes through a slit and then it passes through two slits and finally projects onto a third wall. In the experiment it is shown that radiation when filtered through little holes creates a diffraction pattern that is predictable. Where the concentrated radiation exists, perforations are added to help the radiation pass through.

Secondly, if a series of concentric kiln walls are sequenced in a manner where the front side is reflective and the back side is black and absorbs the heat that is reflected from the next exterior layer, it is possible to move the radiated heat toward the center of the kiln. One simply must create perforations in a manner that are conducive to the diffraction pattern projected onto that layer from behind. Radiation might be concentrated as a concentric ring system, or it may form other geometries. This phenomenon will increase efficiency when operating kilns at higher temperatures.

10.   Reflective Acrylic for Night – Sky Cooling Effect coupled with Thermal Energy Storage Systems

Night Sky Cooling or Radiant Cooling Panels are being developed which operate during the day. The system developed by Stanford University engineers can be viewed in a TED Talk titled, “How We Can Turn the Cold of Outer Space into a Renewable Resource.” Radiant cooling panels interact with the low temperature of space in a manner where heat is radiated into the atmosphere to operate as a heat sink and assist AC systems, thermal energy storage systems and any other mechanical system in need of a very cold heat sink.

In an optimized system a working fluid is employed to transfer additional heat to space. This fluid could be any refrigerant but compressed air with helium at an elevated pressure via a heat pump may be ideal. Most radiative cooling panels are designed more passively, using an incompressible working fluid such as water, but by using compressible fluids such as an air-helium mix, the rate of heat transfer is increased significantly.

The temperature of the background radiation in space is less than 3° Kelvin. The system mentioned that operates during the day employs absorption and reflection for different wavelengths allowing for daytime operation. It absorbs the radiation from space while reflecting the radiation from the sun. The material is a collection of very thin films and is inexpensive for emerging technology.

Acrylic unlike other plastics, does not break down in the presence of sunlight. Acrylic is inexpensive and easy to bend if it is thin enough without the risk of it breaking. There are commercially available versions with a mirror like backing that are inexpensive.

If an extruded parabolic trough is employed as the reflecting surface, acrylic could be laminated onto a structure that is lightweight but stable, installed as a ground mount system and weighed down with sandbags. The surface can then focus radiation to a very high degree on a common pipe made of materials that are very conductive. An example is shown below.

Figure 3a: Radiative Cooling with a Parabolic Trough and Sandbags for the Ballasts.

Figure 3b: Radiative Cooling with a Parabolic Trough and Sandbags for the Ballasts. View 2.

Radiative cooling processes are independent of a medium. Unlike conduction where a break in the material would change the thermal conduction path, radiation is based on heat transfer via the exposure of two surfaces with two different temperatures. Although one cannot change the radiation formula, and the watts/meter-squared achievable is fixed, one can concentrate the radiation into a single area, enabling extreme temperatures to be achieved. This process works both for cooling and heating, which is surprising and groundbreaking.

Keeping this in mind, it is cost effective to send a working fluid through a path equipped with concentrated radiation enabling one to save on piping materials. The working fluid can be directed to a HVAC system or to a thermal energy storage system. To decrease the payback of the system, a heat pump can be employed to compress air mixed with helium, enabling for the difference in temperature to be increased, further allowing for reduced pump flow rates and increased heat transfer.  Whichever material is chosen for the piping; a mix of graphite can increase its thermal conductivity significantly. Helium is recommended as an additive to compressed air systems as well.