The Need for Renewable Fuels
Global warming demands an urgent and thus dramatic change in the current focus and approach of producing energy. Current renewable energy production is mainly focused on solar and wind. However, for many industries their infrastructure is not adapted to electricity as an energy source. Therefore, a full transition to wind and solar is not viable on the short term. More than 50% of the current industry still relies on fossil fuels. This means there is a strong need for renewable fuels, like liquid hydrocarbons, which can directly be applied in the existing infrastructure.
ZEF: Reinventing the Chemical Industry
Zero Emission Fuels (ZEF), a startup focusing on the production of renewable methanol (also a liquid hydrocarbon), aims for a different approach in chemical industry. Current commercial routes to renewable hydrocarbons have not been succesful so far in the global market. By using a scalable number of microplants, opposed to upscaling an industrial size plant, the advantage in terms of cost per kilogram, saving money and time could be significant, because no intensive research and testing regarding upscaling is required. Instead of upscaling the entire plant, simply the number of microplant could be increased to satisfy the renewable MeOH demand. Hence, a small player as ZEF, with fast and cheap growing potential, is able to enter the methanol market by offering renewable methanol at competitive prices of $350/ton in a mainly fossil fuel driven methanol market. ZEF’s product is a fully automated solar panel add-on which converts air to liquid methanol. The microplant extracts H2O and CO2 from the air and uses it to synthesize methanol. This means that CO2 emitted in the atmosphere can be recycled into a renewable fuel. Hence, ZEF poses a solution to close the CO2-cycle. An advantage of the microplant is that it is location independent because water and carbon dioxide are available everywhere. The system is a series of nine subsystems, all of which are based on existing technologies and powered by solar energy. The aim of ZEF is to reach an overall system efficiency of 55%. The numbering-up approach requires the microplant to be suitable for mass-production.
The challenge
The backbone of the microplant is the subsystem which integrates the eight other subsystems. By integrating the different subsystems, the number of parts and thus cost can be reduced significantly. This is a requirement indispensable to the feasibility of the business idea. Thus, the central question in the perspective of the business case and this thesis is to verify whether a reserved budget of EUR 3,5 per backbone is realistic. Is there a backbone which can be designed to correspond to the technical and financial requirements?
Objective
The combination of technical requirements and a tight cost target demands a smart design of the backbone. Therefore, the focus is on product architecture, material choice and mass-manufacturing at a minimal cost. The result is a feasibility study towards the mass-manufacturing aspect applied on the backbone of an energy system. This should all be carried out within the boundaries of the business plan.
Approach
In essence, the feasibility study in terms of a cost analysis is straight forward. A material, volume and production method need to be determined in order to validate the business plan. First, a material needs to be found which is as cheap as possible and complies with the technical requirements. The technical requirements involve coping with aggressive chemicals, elevated temperatures and high pressures. Once a suitable material is found, the volumes are to be looked into. The size of the several subsystems needs to be estimated. Subsequently, a compact layout positioning is needed to minimize the total backbone surface area. Ultimately, the volume is determined by applying a Finite Element Method (FEM) and topological optimization through simulations using Computer Aided Design (CAD) software on the chosen backbone concept. This concept is an approach to integrate all essential functionalities related to the aforementioned other eight subsystems. A prototype of the concept, called the backbone “sample”, has been manufactured by computer numerical controlled (CNC) milling. Finally, a feasibility study was carried out to investigate the possibility for mass manufacturing of the backbone. This feasibility study was based on a cost analysis and on the results of the backbone testing.
Results
The result of this thesis is a product architectural layout applied on a three-plated backbone concept. The CNC-milled prototype (figure c) contains real size partial solutions for all main functionalities of the targeted backbone. These functionalities range from crossing canals subjected to different pressures towards the integration of valves, a buffer and actuators. Hence, the merit of the design is the possibility to copy-paste sub-solutions wherever needed in a future backbone design, even an injection moldable variant. Regarding the cost model, an approach is presented to quickly estimate the material price for a new backbone design. This approach is driven by a fixed amount of material required per functionality. This amount is based upon the material choice and the topology optimization. Regarding testing the CNC-milled backbone sample, the integration of functionalities has proven to be successful. However the custom made seals failed to be leak tight.
Conclusion
The feasibility study of the mass-manufacturing aspect of the backbone based on a cost analysis and results gathered from testing the backbone sample. A cost analysis has been carried out, based on a material suited for mass-manufacturing, design for mass-manufacturing itself and an amount of material necessary. This cost analysis was compared to the target backbone cost defined by ZEF. Based on the developments regarding the entire microplant design of May 2018, the backbone weight is estimated at 7kg and it is made out of the material PET 45% glass fiber (GF). This material is found to be in line with the numerous technical and financial challenges. The weight of 7kg assumes the integration of a 1.3l hydrogen buffer for 1 hour, a 0.7l carbon dioxide-water buffer for two hours, 1.5m piping, 14 one-way partially servomotor controlled valves and three solenoid operated valves. A safety factor of two was applied to guarantee the backbone to be self-bearing and provide support to the subsystems. The final design is a three-plated backbone measuring 200x400mm. Considering a production volume of 500 000 injection mold backbones, one backbone is expected to cost EUR 9,22. Thus, the cost estimation is not in line with the targeted cost of EUR 3,5. Also, regarding testing the backbone sample, the custom made seals have proven not to work. Therefore, the design should be reviewed in terms of weight optimization and detail design. Despite the results, the costs are not far off. Possible opportunities to cut costs are mentioned in the recommendations.
Recommendations
Based on new input of the overall microplant design, the parametric models of the material search and the volume estimation of subsystems, the cost analysis can be adjusted. Hence, these models are a valuable benchmark for further research. Regarding the detail design, it is recommended to work around seals in the next backbone design. These seals are a weak point in the current backbone design and are susceptible to failure. By avoiding seals, the risks with regard to performance and assembly are seriously reduced. Therefore, in a next design step injection molding experts could be approached to help think about a backbone design which is suitable for injection molding without seals.
With respect to the design of the backbone, it is advised to keep cavities as small as possible. For every aspect, which is subjected to higher pressures, ranging from canals to buffers, it must be checked whether it can be reduced in volume. The smaller the pressurized surface area, the lower the stresses on the material, the less material is needed, the lower the backbone cost. Thus, it is recommended to prioritize design for weight optimization in the next backbone design. In relation to weight optimization, design for hybrid materials needs more attention. Other important considerations are mounting the backbone to the solar racking system, cavity creep as a result of a long term load case exposure, permeability of the material with respect to H2 and CO2 and the effect of mutual influences of temperature, chemicals and pressure on the material choice.