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Hybrid tech – get on the bus!

A case study: Cost-benefit analysis - the economics of ultracapacitors


As the world pivots towards sustainable energy solutions, understanding the economic aspects of ultracapacitors becomes imperative. This article delves into the cost-benefit analysis of incorporating ultracapacitors on fully electric buses. This hypothetical scenario investigates the significance of Total Cost of Ownership (TCO) considerations regarding battery systems versus hybrid systems.

 

 

Total Cost of Ownership (TCO) Comparison:

To determine which system—battery-only or a hybrid system combining batteries and ultracapacitors—is more cost-effective over a 15-year period, this case- study considers the following:

1.      Initial Investment: Upfront costs of installing a battery-only system versus a hybrid system that includes both batteries and ultracapacitors.

2.      Operational Costs: Operational expenses, including energy consumption, maintenance, and potential battery replacement costs for each system over the 15-year period.

3.      Benefits of Hybrid System: Benefits of using a hybrid system, such as energy savings (extended driving range due to regenerative braking and improved efficiency), reduced maintenance due to less wear and tear on batteries and brakes, and therefore the extended battery lifespan (the battery life is extended since it avoids frequent deep discharges, which can degrade battery health over time.).

4.      Total Cost Over 15 Years: Cumulative costs for each system over the 15-year period, incorporating initial investments, operational costs, and any other relevant expenses or savings.

 


 

With the adoption of fully electric transport steadily increasing worldwide, this case study provides a snapshot of the potential savings that could be gained through the incorporation of hybrid technology, and how those savings could be further increased with the integration of advanced graphene-based module technology. As seen in the graph above, the Total Cost of Ownership (TCO) for a battery-only system is $4.4 million, with a hybrid system, the TCO is only $4.16 million, and with a hybrid system that uses enyGy ultracapacitors boasting up to double the energy density, the TCO is $3.78 million. At enyGy, we consider innovation not only as the creation of new technology but also as how that new technology can leverage the strengths of and integrate with existing technologies, systems, and processes. One such application of this innovative amalgamation is hybrid technology. 

 

When talking about electric vehicles, a hybrid system combines batteries and ultracapacitors (also known as supercapacitors). While the battery provides what is known as slow energy, the ultracapacitor is a fast energy storage device. The incorporation of ultracapacitors into electric buses leverages the best of both technologies, maximizing efficiency in energy capture and longevity. "It's not about replacing the old with the new; it's about integrating the best of both worlds. That's the philosophy behind the hybrid approach with ultracapacitors," says enyGy CEO, Wiehann de Klerk.

 

The initial cost of ultracapacitors is generally higher than traditional batteries on a per-energy unit basis. This higher upfront cost has been a deterrent for widespread adoption, especially in large-scale applications. For instance, equipping an electric bus solely with ultracapacitors would require a significant capital investment and may not be the ideal solution, especially considering the higher energy density of batteries. That is where combining the benefits of each system into a hybrid system becomes a viable option.

 

 

The hybrid system results in long-term savings due to a host of benefits, including:

 

Energy efficiency:

Ultracapacitors take advantage of energy recuperation opportunities, such as variable speed conditions and periodic stops, through regenerative braking (the reuse of brake heat as energy, typically lost without the means to capture and store it). This translates into fuel savings and reduced wear on braking systems. 

 

Extended lifespan and reduced maintenance:

Ultracapacitors have a longer cycle life (typically between 10-20 years, with up to 1 million charge and discharge cycles) compared to batteries, which degrade over time due to chemical reactions. Ultracapacitors can outlast batteries, reducing replacement and maintenance costs over the long term. Additionally, ultracapacitors can extend the lifespan of batteries themselves because the batteries are not used as heavily as they would be without the ultracapacitors. In practical applications, implementing ultracapacitors for regenerative braking in electric buses has been reported to potentially extend battery life by 10% to 20%.

  



There are many reasons that contribute to the maintenance free nature of ultracapacitors, read further here: Ultracapacitors: No Maintenance. Really? (enygy.com)

 

Operational savings:

Annual energy savings. Real-world applications have indicated potential energy savings ranging from 10% to 25% or even more in certain scenarios.


 Annual maintenance savings:

Maintenance costs for electric motors are much lower because they have far fewer moving parts than conventional motors and are far more efficient.

Implementing ultracapacitors for regenerative braking could potentially reduce brake-related maintenance costs by 30%, due to extended battery lifespan (the battery life is extended since it avoids frequent deep discharges, which can degrade battery health over time).

 

The hybrid system, which combines batteries and ultracapacitors, demonstrates a lower Total Cost of Ownership (TCO) over a 15-year period than the battery-only system. By leveraging improved energy capture, energy savings, extended driving range, and reduced maintenance due to decreased brake wear, the hybrid system emerges as a more cost-effective solution for electric buses in this hypothetical scenario.


The TCO analysis underscores the importance of considering all pertinent factors, extending beyond initial costs, including operational benefits and long-term savings, when assessing the economic viability and efficiency of various energy storage and management systems for specific applications.


Although the upfront investment may exceed that of traditional batteries, the long-term savings, efficiency enhancements, and extended lifespan provide a compelling value proposition.


Ultracapacitors, together with enyGy's patented graphene-based technology, which significantly increases the volumetric energy density of ultracapacitors, are poised to play a crucial role in shaping the future of energy storage and transportation.


 

Acknowledgements


Assumptions and Calculations


Assumptions:

Initial Investment:

  • Battery-only system: $100,000 per bus

  • Hybrid system: $120,000 per bus (additional $20,000 for ultracapacitors to take best advantage of variable speed conditions, periodic stops, and therefore energy recuperation opportunities).

Operational Costs:

  • Electricity Consumption: A fully electric metropolitan bus might consume anywhere from 1 to 1.5 kWh per mile, depending on its efficiency, driving conditions, and passenger load.

    • Electricity Cost: $0.125 per kWh.

    • Miles Driven: A metropolitan bus might drive around 30,000 to 40,000 miles annually, depending on the route and service frequency.

    • Using the above assumptions:

      • Energy consumption per mile = 1.25 kWh (average)

      • Annual energy consumption = 1.25 kWh/mile × 35,000 miles = 43,750 kWh

      • Annual electricity cost = 43,750 kWh × $0.125/kWh = $5,468.75

  • Annual Maintenance: This includes routine inspections, tire replacements, brake servicing, HVAC maintenance, and other minor repairs. Maintenance costs for electric motors is much lower because they have far fewer moving parts than conventional motors and are far more efficient. As a rough estimate, maintenance costs are lower than diesel buses, between $0.20 per mile and $0.40 per mile.

    • Using the 35,000 miles annually:

  • Maintenance cost per mile = $0.30 (average)

  • Annual maintenance cost = 35,000 miles × $0.30/mile = $10,500

Operational Savings:

  • Annual energy savings with the hybrid system: $1,093.75 per bus

    • Real-world applications have indicated potential energy savings ranging from 10% to 25% or even more in certain scenarios. Assuming 20% of $5,468.75.

  • Annual maintenance savings with the hybrid system: $787.50 per bus

    • Implementing ultracapacitors for regenerative braking could potentially reduce brake-related maintenance costs by 30%. Assuming that 25% of the maintenance costs are related to brakes, the calculation would be 30% × (25% × $10,500).

Extended Battery Lifespan:

  • Assume the hybrid system extends the battery lifespan by 15%, reducing replacement frequency and costs.

    • In practical applications, implementing ultracapacitors for regenerative braking in electric buses has been reported to potentially extend battery life by 10% to 20%. Let's assume a 15% extension.

  • Assuming the battery lasts 7-10 years, only one replacement would be required over a 15-year total cost of ownership (TCO). Typically, a metro bus has a lifespan ranging from 12 to 18 years, but for this calculation, we assume a 15-year life.

    • Ultracapacitors do not require replacement due to their high cycle lifetime.

Total Cost of Ownership (TCO) Calculation:

  • Battery-Only System:

    • Initial Investment for 10 buses: 10 buses × $100,000/bus = $1,000,000

    • Operational Costs over 15 Years: 10 buses × ($5,468.75 + $10,500) × 15 years = $2,395,312.50

    • Battery Replacement Costs: 10 buses × (1 battery replacement at $100,000) = $1,000,000

    • Total TCO for Battery-Only System: $1,000,000 + $2,395,312.50 + $1,000,000 = $4,395,312.50.

  • Hybrid System (Batteries + Ultracapacitors):

    • Initial Investment for 10 buses: 10 buses × $120,000/bus = $1,200,000

    • Operational Costs (lower due to energy and maintenance savings) over 15 Years: 10 buses × ($4,375 + $9,712.5) × 15 years = $2,113,125

    • Battery Replacement Costs (Reduced due to extended lifespan – means of included the added benefit of 15% longer lasting battery meaning more time on road earning revenue via fares, etc): 10 buses × (0.85 battery replacements at $100,000) = $850,000.

    • Total TCO for Hybrid System: $1,200,000 + $2,113,125 + $850,000 = $4,163,125.00.

  • Hybrid System (Batteries + EnyGy Ultracapacitors (100% higher energy density)):

    • Initial Investment for 10 buses: 10 buses × $120,000/bus = $1,200,000

    • Operational Costs (double the energy and maintenance savings due to double energy density) over 15 Years: 10 buses × ($3,281.25 + $8,925) × 15 years = $1,830,937.5

    • Battery Replacement Costs (Further Reduced due to further extended lifespan as a result of higher energy density): 10 buses × (0.75 battery replacements at $100,000) = $750,000

    • Total TCO for EnyGy Based Hybrid System: $1,200,000 + $1,830,937.5 + $750,000 = $3,780,937.50.

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