The Dutch utility Eneco and the Danish energy group DONG Energy recently collaborated in building the 870-MW Enecogen Power Station that has a thermal efficiency above 59% and is designed for maximum operational flexibility. As part of Eneco’s strategy to lower emissions across its fleet, the combined cycle plant is designed to quickly compensate for intermittent power produced by the utility’s wind turbines.
Today’s European power generation sector is governed by the need to meet aggressive carbon dioxide (CO2) emission reduction targets. This requirement is making renewable energy sources increasingly important and also driving the need for dependable gas-fired power plants with operational flexibility to balance renewables’ intermittent generation.
With the current lack of energy storage capacity, wind and solar power generation can have fluctuating power levels, depending on when the wind blows and the sun shines. “In the future, combined cycle power plants (CCPPs) will be expected to balance out demand peaks, wind or sunshine shortfalls, and plant outages,” Lothar Balling, head of Gas Turbine Power Plant Solutions in Siemens’ Fossil Power Generation Division, told POWER in July.
On Nov. 11, 2011, the Enecogen CCPP started commercial operations in Rotterdam’s port area after a total construction time of only 31 months. The new plant is able to supply 1.4 million Dutch households with reliable, low-emission power. As joint shareholders of the plant, Eneco, and DONG Energy both sell the electricity and purchase the necessary gas. The partners’ total investment in the facility is just under €700 million ($863 million).
Balling said that CCPPs’ increased use for power generation over the past decade stems from their high efficiency, rapid construction and commissioning times, and relatively low specific investment costs compared with other generation facilities such as coal-fired units, nuclear, or hydro. But now the potential for fast startup, load ramping, and grid stabilization support are also becoming increasingly important for complementing intermittent renewables. With its excellent efficiency record, the Enecogen plant is an example of a state-of-the art CCPP.
“This new power plant impressively demonstrates how assured supply, operating economy, and environmental compatibility can be harmonized,” said Balling.
The facility achieves a net fuel efficiency of more than 59% at an ambient temperature of 11C, a relative humidity of 75%, and a cooling water temperature of 12C. The plant’s two 435-MW single-shaft units (steam turbine and combustion turbine are arranged in a common driveline with a double-ended generator in the middle) are designed for 290 starts per year.
“After the start command, the full power output is available after 50 minutes if the units are still warm. If the units have been at standstill for less than eight hours—called a hot start—the synchronization with the grid will be reached within 15 minutes,” Balling said.
The plant’s other achievements include low noise levels and no fine particulate emissions. In addition, its ammonia-based selective catalytic reduction technology reduces the nitrogen oxide (NOx) emissions significantly and transforms NOx emissions into nitrogen and water that evaporate via the stack.
As part of a turnkey project, Siemens built, delivered, and commissioned the plant’s main components. Each of the two single drivelines consists of a gas turbine (SGT5-4000F), hydrogen-cooled generator (SGen5-3000), and steam turbine (SST5-5000) (Figure 1). In addition, the innovative instrumentation and control system (SPPA-T3000) is from Siemens. The German company signed a long-term service agreement for these components.
|1. Successful teamwork. Inside the 870-MW Enecogen combined cycle power plant you find a SGT5-4000F gas turbine (right), a SGen5-3000W generator (middle), and an SST5-5000 steam turbine (left) arranged on a single shaft. Courtesy: Enecogen|
The Dutch boiler supplier NEM built the conventional three–pressure level heat recovery steam generator. The following companies handled the project’s civil construction: Terracon (piling), Porr (concrete works), ASK Romein (steel structures), and BAM (cooling water inlet and outlet structures).
The site is ideal for an electric plant for the following reasons:
- Especially developed for industrial use.
- Abundant cooling water availability.
- Proximity to high-voltage grid and to high-pressure gas grid.
- Energy savings and CO2 emission reduction through possible future collaboration with nearby industries.
Enecogen is now connected through a 12-kilometer-long underground high-voltage cable to the Maasvlakte substation, which is part of the national grid. Gas Transport Services, the national network operator for gas transport services, takes care of Enecogen’s gas connection.
Currently, 38 plant employees handle the plant’s ongoing operations and maintenance. Looking ahead, Enecogen management is searching for opportunities to collaborate with surrounding industries.
Conquering Construction Hurdles
The challenges during plant construction covered a wide spectrum. For example, because the plant site is located in an area that had World War II combat operations, the construction crew had to look for possible unexploded ordnance (UXO) during piling, excavation, and other earthwork. Although construction workers found some UXO, it was handled carefully, and there were no accidents.
Another obstacle involved nearby oil pipelines. The project team had to connect four cooling water pipes (two in and two out) to the Beerkanaal (Beer Channel), in Rotterdam harbor. To reach the Beerkanaal, the four pipes had to cross three existing oil pipelines owned by the neighboring BP Refinery Rotterdam (two 42-inch pipelines containing crude oil and one 16-inch pipeline containing fuel oil). These pipelines connect the BP Refinery Rotterdam to the MOT (the terminal on the Maasvlakte). The Encogen project team diligently identified existing pipeline locations and selected the location of the new pipelines to ensure that construction operations did not adversely impact BP’s oil pipelines.
“In the early stages of the project, the Enecogen project team contacted BP Refinery Rotterdam. Together we discussed the risks and determined which way the crossings had to be constructed in order to make them safe,” Maintenance Engineer Leon Lurken said. “The agreement on risk mitigation and construction methods was formalized in a contract signed by all the parties.”
After the subcontractor BAM made a detailed design for the crossings and BP Refinery Rotterdam and Enecogen agreed on the safety aspects, risk assessment, construction, and monitoring plan, BP Refinery Rotterdam representatives gave their approval to start constructing the crossings.
Despite these challenges, the project team completed construction with excellent safety statistics: only two lost-time incidents with slightly over 2 million man-hours worked. During the project’s construction period, approximately 920 employees employed by more than 30 contractors worked at the site. The project included installation of 9,700 tons of machinery, 1,000 tons of pipelines, 2,500 tons of steel, 23,000 cubic meters of concrete, and 300 kilometers of cables.
Eneco is the largest Dutch-owned energy company. Its integrated distribution operation covers the generation, transmission, supply, metering, and billing of gas, electricity, and heat for 2 million customers. By 2030, Eneco’s energy mix will consist of several types of sustainable sources of electricity, heat, and gas. The company is investing in solar energy, biomass power, and wind energy in various western European countries.
One of the leading energy groups in northern Europe, DONG Energy is headquartered in Denmark. Its business is based on procuring, producing, distributing, and trading in energy and related products in northern Europe. Besides the Enecogen CCPP, DONG Energy’s other Dutch activities and assets include ownership in the GATE LNG Terminal in Rotterdam, which is under development and situated across the harbor inlet from the Enecogen plant.
By building the Enecogen plant, Dutch Eneco and Danish DONG Energy are promoting their mutual goal of providing clean and reliable energy to the Netherlands while seeking to make profitable returns on their joint investment.
“We are very pleased with this new plant, which is fully in line with our strategy to improve the sustainability of the energy supply,” said Jeroen de Haas, Eneco CEO. “Enecogen improves our ability to balance the fluctuations in the electricity produced by our wind farms.”
As is Eneco, DONG Energy is trying to cut CO2 emissions in its overall fleet by adding new gas and biomass-fired power plants and offshore wind farms. The Enecogen facility fits into its plan to promote sustainable energy. Besides its Dutch holdings, it owns power generation facilities and projects in Germany, Sweden, Norway, and the UK.
DONG Energy’s goal is that by 2020, renewables will supply the energy for approximately 50% of its heat and power production. Looking ahead very long term, the company’s ambition is that by 2040 around 85% of its electricity and heat generation will come from renewable energy.
— Angela Neville, JD is POWER’s senior editor.