Solar Energy System of the Month - the Martin Next Generation Solar Energy Center

2011-04-12

It could be a scene from one of a number of locations around the world. Sprawled over more than 2 square kilometers of agricultural land, rows of enormous curved mirrors shine in the afternoon sun, concentrating light onto a synthetic oil in a tube that will be used to generate power.

However, this time, the rows of curved mirrors sit next to another set of structures: a row of five tall edifices housing 3.8 GW of natural gas turbines.

Construction of the Martin Next Generation Solar Energy Center. Solar Server's April 2011 Solar Energy System of the Month. Courtesy of FPL
Construction of the Martin Next Generation Solar Energy Center. Solar Server's April 2011 Solar Energy System of the Month. Courtesy of FPL

Also, this scene is not in California's Mojave Desert, Spain, or even Australia. This plant lies in Central Florida, thousands of kilometers from any other CSP plants, as the only commercial-scale operational CSP plant in the United States east of the Rocky Mountains.

Florida Power and Light Company's (FPL, Juno Beach, Florida, U.S.) novel concentrating solar power (CSP) / natural gas hybrid is a groundbreaking plant that challenges a number of the current assumptions about these technologies, and points to a way for greater integration of CSP with existing power sources. For these reasons, the Martin Next Generation Solar Energy Center is Solar Server's April 2011 Solar Energy System of the Month.

 

Developing the Martin Next Generation Solar Energy Center

The Martin Next Generation plant is a hybrid where 75 MW of parabolic trough CSP supplies heat to accompany natural gas generation. The plant consists of a field of 190,000 curved mirrors, which concentrate light to heat a synthetic oil to temperatures of 398 degrees Celsius, which is fed to four combined cycle natural gas units. These natural gas units have a total output of 1.1 GW.

The CSP component is a retrofit on the natural gas plant. FPL began incorporating the CSP component of the plant in December 2008. FPL commissioned this new hybrid portion of the plant in December 2010, after making physical connections to the existing feedwater, main steam, reheat steam, electrical, and digital control systems.

While the project was completed ahead of schedule, FPL states that there  were "numerous" challenges overcome regarding control system tuning related to heat transfer fluid flow and temperature control, as well as HRSG drum level control.

Originally forecast to cost USD 476 million, the plant came in under budget at around USD 400 million. FPL estimates that the construction process created more than 1,000 direct jobs.

 

Advantages of the hybrid design

Engineers state that the retrofit of fossil fuel generation to incorporate CSP has technical advantages. As opposed to building a new CSP plant, there is no need to purchase and install new turbines and other power generation infrastructure, and FPL has stated that the cost of integrating the solar field is 20% less than building a stand-alone CSP facility.

Aerial view of the Martin Next Generation Solar Energy Center. Courtesy of FPL
Aerial view of the Martin Next Generation Solar Energy Center. Courtesy of FPL

FPL states that the integrated unit is "much more efficient" when operating, offsetting the need for additional natural gas. FPL estimates that the addition of the solar field will reduce natural gas usage at the plant by 1.3 billion cubic feet (37 billion cubic liters) per year, for a total of 41 billion cubic feet (1.2 trillion cubic liters) over the lifetime of the plant.

FPL states that the plant will supply electricity to its customers at a cost of USD 0.16/kWh over the life of the plant. While this is higher than natural gas generation, is lower than many solar plants. In an analysis of the plant, Greentech Media has also noted the extra cost of hurricane protection for the CSP field, which includes a feature where the collectors can turn upside down if a hurricane approaches.

 

CSP and fossil fuels

This is not the first foray into CSP for FPL's parent company, NextEra Energy Inc. (Juno Beach, Florida, U.S.). NextEra is the co-owner of the Solar Energy Generating Systems (SEGS) in California's Mojave Desert, which were among the first CSP plants built in the world from 1984-1991.

Nor is this the first time that CSP has been combined with natural gas. A number of existing CSP plants incorporate natural gas backup generation to supply power during cloudy periods and to allow the plants to operate on-demand. However, what is different about the Martin Plant is that the CSP supports the natural gas generation, not the other way around.

A number of other combined fossil fuel/CSP plants are either in construction or operational in other parts of the world. In Australia, the Liddel coal plant uses linear Fresnel CSP to heat incoming water, and in the U.S. State of Colorado, Xcel Energy has tested the concept of using CSP to accompany coal generation at its Cameo Generating Station. However, in both cases the capacity of the solar generation is much smaller in comparison to the fossil fuel generation capabilities.

Construction of the Martin Next Generation Solar Energy Center. Courtesy: FPL
Construction of the Martin Next Generation Solar Energy Center. Courtesy: FPL

 

From Florida to Morocco

FPL has stated that it currently has no plans to replicate the design of the Martin plant in other areas, citing "regulatory constraints". However, the idea of combining CSP and natural gas generation has caught on in other parts of the world, particularly North Africa.

The Kuraymat plant, Egypt. Courtesy of Drehmo
The Kuraymat plant, Egypt. Courtesy of Drehmo

The first large CSP/natural gas hybrid plant to be completed in November 2010 was the Ain Beni Mathar Plant in Morocco, which was designed with 30 MW of CSP accompanying 470 MW of natural gas generation.

Similar natural gas / CSP hybrid plants are also under construction in Egypt (Kuraymat) and Algeria (Hassi R'Mel), as well as in Northern Mexico (Agua Prieta). 

It is significant to note that CSP and solar photovoltaics (PV) have been advanced in the most affluent Western nations, led by Europe, the United States, and Japan, whereas combined CSP/fossil fuel generation is making inroads in less affluent regions that have little PV and no CSP capacity.

The use of hybrid CSP/natural gas plants may also lead to greater use of CSP technology in these regions. The nation of Morocco has plans to increase the solar field capacity at its Ain Beni Mathar plant, as well as to build a number of CSP plants.

In this way, the Martin Next Generation Solar Energy Center as a working model for combined CSP and natural gas generation is significant for regions of the world far beyond Florida, and may be an important step for the future for CSP technology.