Tight energy supply conditions and renewable energy project delays have led two Wisconsin utilities to delay the retirements of several coal-fired units.

We Energies said it will extend the lives of four units at its Oak Creek site. The coal units have a total capacity of 1,100 MW and were placed into service in the late 1950s and 1960s.

The expected retirement of Oak Creek Units 5 and 6 will be delayed by one year, until May 2024. The retirement of Units 7 and 8 will be delayed for approximately 18 months, until late 2025.

“The decision to postpone the retirement dates for these units is based on two critical factors: tight energy supply conditions in the Midwest power market and supply chain issues that will likely delay the commercial operation of renewable energy projects that are currently moving through the regulatory approval process,” said Scott Lauber, president of We Energies.

Alliant Energy also plans to push back the retirement of Edgewater Generating Station in Sheboygan to a new date of June 2025. The remaining Edgewater unit has a roughly 400 MW capacity and was commissioned in 1985. The plan was originally to retire Edgewater by the end of 2022.

The utility also said the remaining Columbia Energy Center units in Portage will now be retired by June 2026. Columbia went into operation in 1975 and is capable of generating more than 1,100 MW at capacity. The plant was scheduled to close by the end of 2024.

David de Leon, president of Alliant Energy’s Wisconsin energy company, said the decision to delay the retirements also stems from supply chain and economic challenges, along with shifting Midcontinent Independent System Operator (MISO) requirements beyond 2022 and regional short-term reliability concerns.

MISO recently released a study forecasting the region, which includes parts of 15 states including Wisconsin. The study said MISO could face energy shortages during the summer of 2022.

Alliant Energy said it expects to be out of coal generation in Wisconsin by mid-2026. The company is currently moving forward on 12 solar projects that will bring nearly 1,100 MW of generation online in the state.

We Energies has a goal to reduce carbon emissions from its generating fleet by 60% at the end of 2025 and 80% by the end of 2030. Both measures are compared to a 2005 baseline.

We Energies and Wisconsin Public Service, both subsidiaries of the WEC Energy Group, announced in 2021 they were jointly planning to build 625 MW of combined solar and energy storage capacity in the state.

The utilities proposed the 325 MW Darien Solar Energy Center and storage project in Rock and Walworth counties. The $446 million site would feature 250 MW of solar generation linked to 75 MW of battery storage. Construction was expected to begin in Spring 2022 with completion by the end of 2023

The companies also announced plans for the 310-MW Paris Solar-Battery Park. The $400+ million Paris project will be built in Kenosha County, Wisconsin. It was approved by regulators in March.

WEC Energy Group (WEC), Wärtsilä, the Electric Power Research Institute (EPRI) and Burns & McDonnell will partner to carry out hydrogen fuel testing in reciprocating engines at the A.J. Mihm power plant in Michigan.

WEC’s 55 MW plant currently operates with three Wärtsilä 50SG engines that run on natural gas. It was placed into service in March 2019.

The parties will aim for testing fuel blends of up to 25% hydrogen volume mixed with natural gas.

Wärtsilä said the engines can operate with this level of hydrogen blend with little or no modifications needed.

One engine will be selected for the test program and will continue to deliver power to the grid. The hydrogen content in the fuel will be gradually increased to 25%, with measurements of the engine’s performance made throughout the testing.

Wärtsilä said it has already hydrogen blending tests at facilities in Vaasa, Finland and Bermeo, Spain.

The project aims to support WEC’s goal of reducing carbon emissions 60% (from 2005 levels) from its generating fleet by the end of 2025. It could also inform similar hydrogen blending efforts in other reciprocating engines.

Each of Wärtsilä’s three engines at A.J. Mihm has its own 65-foot stack and are cooled by 24 radiator fans that reject heat from a closed-loop circulating antifreeze (coolant) system.

Fueled with natural gas, each engine is shaft-coupled to an electric generator. The units are housed inside a building with an exterior resembling a warehouse. The exhaust system is located outside the building and includes silencers, air quality control systems and stacks.

The plant uses selective catalytic reduction with urea injection for control of nitrogen oxides and an oxidation catalyst for control of carbon monoxide, volatile organic compounds and hazardous air pollutants.

“These hydrogen tests reinforce the viability of the internal combustion engine as a future-proof technology that plays a key role in decarbonizing the power industry,” said Jon Rodriguez, director for engine power plants at Wärtsilä North America.

During the pilot project, hydrogen and natural gas will be mixed up to a 25/75 percent blend to power one of the generating units that serves customers of Upper Michigan Energy Resources, a WEC energy subsidiary. The units use reciprocating internal combustion engines, which were manufactured by technology company Wärtsilä and began service in 2019.

Reciprocating engines convert pressure into rotating motion using pistons, while gas or combustion turbines use the pressure from the exploding fuel to turn a turbine.

WEC is partnering with the Electric Power Research Institute (EPRI), which will lead the technical implementation of the project and share results to further educate the energy industry about how to successfully use hydrogen for power generation to support reducing carbon emissions.  

WEC described the hydrogen power pilot as among the first of its kind in the U.S.

“The potential of adding hydrogen as a clean generating fuel to our fleet of dispatchable plants is an important step as we bridge to a bright, sustainable future,” said Gale Klappa, executive chairman

WEC Energy Group has a goal of net-zero carbon emissions from electric generation by 2050 and net-zero methane emissions from natural gas distribution by the end of 2030.

In 2020, Wärtsilä said it was developing the combustion process in its gas engines to enable them to burn 100% hydrogen fuel. At the time it had tested its engines with blends of up to 60% hydrogen and 40% natural gas.

In addition to hydrogen, it said other potential renewable fuels also were being studied for future applications, that its engines were already capable of combusting 100% synthetic carbon-neutral methane and methanol.

The U.S. Department of Energy identifies two primary reciprocating engine designs relevant to stationary power generation applications: the spark ignition Otto-cycle engine and the compression ignition Diesel-cycle engine.

The essential mechanical components of the Otto-cycle and Diesel-cycle are the same. Both use a cylindrical combustion chamber in which a close fitting piston travels the length of the cylinder. The piston connects to a crankshaft that transforms the linear motion of the piston into the rotary motion of the crankshaft. Most engines have multiple cylinders that power a single crankshaft.

The main difference between the two cycles is the method of igniting the fuel. Spark ignition engines (Otto-cycle) use a spark plug to ignite a pre-mixed air fuel mixture introduced into the cylinder. Compression ignition engines (Diesel-cycle) compress the air introduced into the cylinder to a high pressure, raising its temperature to the auto-ignition temperature of the fuel that is injected at high pressure.

For combined heat and power applications, most installations use four-stroke spark ignition engines, the Energy Department said. Reciprocating engines are characterized as either rich-burn or lean-burn. Rich-burn engines are operated near the stoichiometric air/fuel ratio, which means the air and fuel quantities are matched for complete combustion, with little or no excess air.

In contrast, lean-burn engines are operated at air levels significantly higher than the stoichiometric ratio. In lean-burn engines, engine-out NOx emissions are reduced as a result of lower combustion chamber temperatures compared to rich-burn engines.