«Quadrennial Technology Review 2015 Chapter 6: Innovating Clean Energy Technologies in Advanced Manufacturing Technology Assessments Additive ...»
A challenge for heat exchangers when working with low temperature fluids is the large heat transfer area required, especially if heat is to be recovered from gaseous exhausts. Developments that increase heat transfer coefficients in heat recovery systems could partially address this issue. Some examples of commercially available technology for improving heat technology coefficients are ceramic inserts used in radiant heating tubes, dimpled or finned tubes, and heat pipes. Further information on research needs for low temperature waste heat recovery can be found in the “Waste Heat Recovery” technology assessment.
Smart CHP Systems CHP has the potential to play a significant role in the modern smart grid. Integrating manufacturing operations and CHP into the modern grid system will allow manufacturers to enjoy the cost savings from increased energy efficiency and will also provide the potential to realize additional revenue streams. The focus of longerterm research on grid integration and smart CHP systems will be to fully incorporate smart manufacturing operations, including smart CHP, into an optimized grid. This will involve examining industrial electrical and thermal loads and how they can be incorporated into electricity markets, with the objective of optimizing system efficiency, utilization, and cost-effectiveness.
Program Considerations to Support R&D Historical Investments in CHP
The DOE CHP R&D portfolio has included the following:
Advanced reciprocating engine systems (ARES): The goal of the ARES program was to deliver a technologically advanced engine/generator system that combined high specific power output and low exhaust emissions with world-class overall efficiency while maintaining excellent durability, all at a low installed cost.
This program demonstrated improved engine electrical efficiencies, increasing from ~35% at project start to 50% on project closure—a nearly 50% increase.
Packaged CHP systems: The development of packaged CHP systems suitable for smaller industrial facilities can enable users to avoid complicated and costly system integration and installation but still maximize
performance and increase efficiency. The projects included the following:
High efficiency microturbine with integral heat recovery39
High value applications: New high-value CHP technologies and applications can offer attractive end-user
economics and significant energy savings with reproducible results as follows:
Flexible distributed energy and water from waste for the food and beverage industry Microchannel high-temperature recuperator for fuel cell systems Novel controls for economic dispatch of combined cooling, heating, and power systems
16 Quadrennial Technology Review 2015 TA 6.D: Combined Heat and Power Fuel-flexible CHP: Accelerating market adoption of emerging technology and fuel options can improve industry competitiveness through more stable energy prices, cost savings, and decreased emissions. Examples of these technology and fuel options include biomass gasifiers, gas turbines utilizing opportunity fuels, landfill
gas cleanup and removal systems, and desulfurization sorbents for fuel cell CHP as follows:
Adapting on-site electrical generation platforms for producer gas Development of an advanced CHP system utilizing off-gas from coke calcination Development of fuel-flexible combustion systems utilizing opportunity fuels in gas turbines Integrated CHP/advanced reciprocating internal combustion engine system for landfill gas to power
Demonstrations: The installation of innovative technologies and applications that offer the greatest potential for replication can provide compelling data and information to foster market uptake in manufacturing and
other applications as follows:
ArcelorMittal USA blast furnace gas flare capture43 BroadRock renewables combined cycle electric generating plants fueled by waste landfill gas44
R&D opportunities and research targets for the development of CHP and ultrahigh efficiency generation technologies are shown in Table 6.D.5.
17 Quadrennial Technology Review 2015 TA 6.D: Combined Heat and Power Table 6.D.
5 Strategic R&D Opportunities and Performance Targets for CHP
Risk, Uncertainty, and Other Considerations Technical Risks The long-term development of highly efficient and more broadly applicable types of CHP systems and technologies involves several areas of technical risk. Thermodynamic optimization of systems with multiple outputs is challenging, and significant barriers exist.
Some of these technical risk areas relate to system size (scale), individual cycle development, and combined cycle integration as follows:
- Scale matters for combustion systems because of fundamental physics or because of economics of optimization. In order to achieve broader adoption of CHP in markets with significant remaining 18 Quadrennial Technology Review 2015 TA 6.D: Combined Heat and Power
- Biggest issues are economical materials that can operate at higher temperatures and resist corrosion.
The challenge will involve identifying and developing materials that can withstand these conditions while maintaining competitive system costs.
- Some devices would need development to pair well with others (e.g., current pressurization levels for molten carbonate fuel cells (MCFC) may be less viable than for solid oxide fuel cells for operation with a gas turbine).
- Balance of power distribution between cycles and optimization of internal mass and heat flows can be challenging.
- Individual system efficiencies are not superimposable for combined system efficiency.
- Some cycles may not be at highest individual efficiency when integrated.
Market Risks While CHP systems sized according to the thermal demand of a facility are cost-effective and have been broadly deployed in the 5 MW size ranges, there are a host of policy and regulatory barriers that limit further deployment in the marketplace.48 These barriers limit the ability for CHP to succeed in energy services markets.
Fully integrating CHP into the modern local grid or facility cluster will allow manufacturers and other facility operators to enjoy the cost savings from reduced on-site fuel consumption and will also provide the potential to realize additional revenue streams. In a truly integrated and smart grid, a facility may be able to participate in ancillary service markets, enhanced demand-response programs, and other alternate revenue-generating schemes. Ultimately, grid integration of next-generation CHP-based distributed generation will result in stronger, more profitable, and more resilient operations for both the utility and end-use sectors.
Furthermore, the ability to size a CHP system to the needs of the local grid system (versus sizing to satisfy the thermal demand of a particular facility) would allow a broader array of facility types to install CHP.
This is particularly applicable to some of the larger types of CHP facilities in the manufacturing sector, where very large thermal demands result in systems that produce more electricity than can be used on site. Interconnection rules and reasonable buy-back rates (which were established in 1978 under the Public Utility Regulatory Policies Act – PURPA) can alleviate this situation but only in a limited way that is dependent on local utility and regulatory policy. Additional discussion of barriers and opportunities is found in the subsequent section on “Market Risks.” 19 Quadrennial Technology Review 2015 TA 6.D: Combined Heat and Power Case Study Case Study: CHP in Food Processing Industry—Frito-Lay Demonstration49 Frito-Lay North America, Inc., installed a CHP system at its food processing plant in Killingly, Connecticut, in April 2009. The installation was supported by funds from DOE in partnership with the Energy Solutions Center as well as incentives from the State of Connecticut. In order to reduce the energy costs and environmental impact of the Killingly plant while easing congestion on the
constrained northeast power grid, Frito-Lay installed the following:
A 4.6 MW Solar Turbines Centaur® 50 natural gas combustion turbine
The CHP system, designed to be electric-load following, has the capacity to meet 100% of the plant’s electrical power needs and provide a majority of the facility’s annual steam needs.
Converting Waste Heat into Steam Before the installation of the CHP system, the Killingly plant steam requirements were provided by three dual-fired (natural gas and residual oil) boilers. The three boilers were over 30 years old, and if one boiler needed service, the remaining two boilers could no longer meet the plant’s peak steam load.
The CHP system can now provide about 80% of the steam load for the Killingly facility (Table 6.D.6).
6 Estimated benefits from the CHP at the Killingly plant.
20 Quadrennial Technology Review 2015 TA 6.D: Combined Heat and Power Running in Island Mode The Killingly plant—which operates 24/7—has the capability to run in island mode by using the CHP system if the power grid goes down. In 2009 and 2010, flying squirrels shorted out local service, leaving the entire area without power for hours. However, Frito-Lay’s CHP system continued operating— for six hours in the first incident and eight hours in the second—allowing the plant to maintain production. This added power reliability avoided product losses and prevented the need for food safety reinspections, resulting in significant cost savings.
The ability to run in island mode also means that the plant is less susceptible to outages caused by severe storms. The Killingly plant was intentionally powered down one day prior to Tropical Storm Irene in 2011. Three days after the storm, more than 60% of Killingly remained without power, but with the CHP system, Frito-Lay was quickly able to resume production less than 24 hours after the storm had passed.50 The Killingly plant also remained operational during a late October 2011 snowstorm that had knocked out power to nearby areas. The plant could also have continued operat-ing during Superstorm Sandy in October 2012 and a blizzard in February 2013 if the roads had not been shut down by the governor.
21 Quadrennial Technology Review 2015TA 6.D: Combined Heat and Power
Appendix: High-efficiency distributed electrical generation notes and calculations Discussion of Table 6.D.3 and Figure 6.D.7 In this CHP Technology Assessment, Table 6.D.3 and Figure 6.D.7 describe a number of different single and combined cycles. The following discussion describes some of the analysis and some of the assumptions made as well as any references. The letter refers to the last column of Table 6.D.1, labeled “Notes.” Gas thermodynamic and transport properties were derived from the NIST Reference Fluid Thermodynamic and Transport Properties Database, commonly referred to as REFPROP.51 These properties were used as inputs into our analysis. In all cases, standard ambient conditions were used as the reference ambient state.
A: Gas turbines (GTs) on the lower end of power output (e.g., 5 MW) are generally less efficient than largecapacity turbines. Large-scale GTs can have 10 percentage points higher efficiency than smaller-scale GT systems; much effort and expense are spent on optimizing the heat balance with techniques such as reheat and recuperation. Several proposals include steam injection (e.g., the humid air turbine), which can increase system efficiency by 5–10 percentage points. However, these can consume large volumes of high-purity water with additional capital and operating costs. The wide range of performance for single-cycle GTs showed results from different operating strategies and design configurations. When coupling a system with a Rankine cycle (RC), it generally is assumed that a hotter input gas stream (i.e., exhaust-gas temperature) yields higher efficiencies.