Navigant Research Blog

Why Does Diesel Win in Places like Puerto Rico? It’s 9,000 Times Better Than Solar PV by This Metric

— December 12, 2017

In the aftermath of natural disasters like Hurricane Irma, there is much talk about how renewables are the ideal backfill to replace and modernize electric grids. Indeed, renewables like solar PV and wind, along with energy storage, grab headlines due to their falling costs, low lifetime carbon emissions, and general excitement about their deployment and future potential. Why, then, was the largest immediate post-storm addition a pair of 25 MW diesel-fired turbines installed by APR Energy?

Compactness Is Key

In addition to dispatchability and fast install (the plant was operational in 15 days), a key factor is energy density, defined here as daily energy output per acre of plant area. By Navigant Research numbers, combustion turbines like the ones installed by APR can produce as much as 6,200 MWh in a day using 1 acre of land. Compare that to solar PV, which is smaller by a factor of 9,200; based on National Renewable Energy Lab data, solar PV can be expected to produce about 0.67 MWh in an acre. The figure below indicates energy density by corresponding bubble size. The numbers vary by project, but the contrast is stark. Reciprocating generator sets (gensets) are compact, more distributed than the turbines, and a key part of the recovery (with the installation of 375 generators noted by this article). There are also headlines citing fast installation of renewables in microgrids, a clear trend of the future. Still, many of the high output, dense systems tend to be based around fossil fuels.

Energy density has two components. Power density (along the vertical axis) indicates the footprint needed for energy production in any instant of time. Combine that with the second component—capacity factor, along the horizonal axis—and fossil-fueled generation can look exceptionally appealing thanks to its availability nearly 24/7. A crucial advantage is the system’s dispatchability, the ability to provide power on demand.

Energy and Power Density by Technology: Daily Delivered Energy (MWh) in 1-Acre Footprint,
North America: 2017

*Assumes 6-hour (150 MWh) battery discharges 80% of capacity, once daily.

**Equivalent hours/day at max output, assuming consistent demand for power.

Sources: Bloom Energy, Caterpillar, General Electric, National Renewable Energy Laboratory, NGK

Island nations are often constrained on space and need to fit generation among existing infrastructure—especially after a disaster. Many are among the most cramped on Earth, with Japan, Taiwan, the Philippines, Puerto Rico, and many Caribbean nations falling in the top one-sixth of all countries by population density. Though rooftops are available for solar PV, they can be small and may need retrofits. Offshore wind is quickly becoming more appealing, too (though if the grid goes down, it can’t provide onsite, distributed power).

Hybrid Systems Hold Promise

While diesel has the advantage of compactness and dispatchability, it is also expensive, challenging to transport long distances, and emits lots of greenhouse gases and other criteria pollutants like NOX and particulate matter. Natural gas holds many of the same advantages while avoiding many of the cons of diesel; where it is available, it often outperforms diesel. Dual-fuel turbines and gensets can be even more attractive—the Puerto Rico turbines produce power at 18.15 cents/kWh on diesel and less on natural gas when it’s available.

Still, natural gas faces similar hurdles to those noted for diesel (albeit lower ones). In many cases, the optimal system is hybridized—relying on a mix of fossil fuel and renewables. Despite all the buzz around solar, storage, and other renewables, reliance on only those technologies is often cost prohibitive. Hybrid microgrids based around diesel or heavy fuel oil generation can often see fuel savings of 10%-30% or more with the addition of new technologies like solar PV, wind, and storage.


Preparing for the Worst, Cities Seek Resilience

— August 7, 2014

The Rockefeller Foundation is asking cities to apply for the latest phase of its 100 Resilient Cities Centennial Challenge.  This challenge aims to enable 100 cities to better address the shocks and stresses of the 21st century.  The selected cities receive support from the Rockefeller Foundation to create and implement resilience plans and to hire chief resilience officers (CROs) to oversee strategies.  Thirty-two cities – including, for example, Bangkok, New Orleans, Durban, Mexico City, and Rotterdam – were selected in the first phase of the competition.  San Francisco appointed the first CRO in April 2014.

The Intergovernmental Panel on Climate Change’s 2014 report on the impacts of global climate change highlights the particular vulnerability of urban infrastructures.  The impact of climate change on cities can take many forms – including increased temperature, drought, and storms – but the most direct threat comes from rising sea levels.  Approximately 360 million urban residents live in coastal areas less than 10 meters above sea level.  China alone has more than 78 million people living in vulnerable, low elevation cities.  Miami, New York City, and Tokyo are also among the top 20 cities at the highest risk of coastal flooding, along with Asian megacities such as Mumbai, Shanghai, Bangkok, and Dhaka.   The 2011 Tohoku earthquake and tsunami in Japan and Hurricane Sandy off the East Coast of the United States in 2012 demonstrated how even the most advanced cities can be devastated by extreme events.

After the Flood

The threat to American cities is further emphasized in the Third National Climate Assessment from the U.S.  Global Change Research ProgramMiami, in particular, is developing into a test case for the impact of the climate changes on U.S. cities and the ability of civic and business leaders to collaborate in response.

Resilience can be characterized as the ability of cities and communities to bounce back from catastrophic events, as well as respond to more gradual changes that threaten well-being or economic stability.  Resilience is not just a question of identifying and acting on specific climate change impacts; it also requires an assessment of each city’s complex and interconnected infrastructure and institutional systems.   New York, for example, initiated a major study of the how the city’s infrastructure and services can be better designed to cope with events like Hurricane Sandy – including more resilient, distributed energy grids and new approaches to land use policy in flood-prone areas.

Urban Sensitivities

Resilience is also a driver for new technology adoption.  The Sensing City project in Christchurch, New Zealand is an interesting test case for how smart city technologies can support resilience planning.  Christchurch was devastated by an earthquake in 2011 that left 185 people dead; the rebuilding project is estimated to eventually cost around NZ$40 billion ($35 million) in total.  The aim of Sensing City is to use sensor technologies and data analytics, including smartphones and sensors embedded in new construction, to lay the foundation for a healthier, more sustainable, and more resilient city.

Coping with the threats and uncertainties of the 21st century will require a deeper understanding of the normal operations of a city and its vulnerabilities.  That’s why resilience is becoming one of the key attributes of any smart city and a significant driver for the smart city market.


Philippine Typhoon Highlights New Disaster Risks

— November 15, 2013

An odd combination of distance and familiarity allows people living comfortably in the West to shrug and turn away from the devastation of Typhoon Haiyan in the central Philippines.  An island country on the other side of the world is, once again, struck by a massive natural disaster, apparently the act of a wrathful God.  What’s new?  Like earthquakes in Central Asia, the incomprehensible scale of the destruction provokes a brief outpouring of compassionate aid, and not much else.  The modern world goes back to getting and spending.

Two things are changing, though, that make that “What can you do?” response less tenable.  For one thing, there’s a growing realization that such disasters are not just “natural.”  Second, they are coming soon to a coastline near you.

In the Red Zone

Drawing on a 2003 book titled At Risk: Natural Hazards, People’s Vulnerability, and Disasters, by Ben Wisner and three co-authors, Tim Kovach writes, “Let me be blunt: there is no such thing as a ‘natural’ disaster.”  A disaster requires at least three variables: a powerful natural event, a vulnerable population living in a hazardous area, and socioeconomic factors that increase the risk of exposure and limit the ability of the affected communities to recover.  If a typhoon levels an uninhabited island in the South China Sea, it’s not a disaster; it’s a noteworthy meterological event.  When it affects more than 11 million people, most of them living in flimsy wooden houses with no protection from powerful weather (and little help from their central government, housed in a modern city on a distant island), it’s a disaster.

The Philippines, with its 7,000 islands, volcanoes, mountainous jungle, exposure to the South Pacific, and endless, tropical coastline, is basically one big hazard zone.  On the other hand, as The Huffington Post, pointed out in a lengthy report one year ago, the United States has by choice funded rampant development in coastal “red zones” that are vulnerable to increasingly violent storms, as the $65 billion in damage from Tropical Cyclone Sandy amply demonstrated.  The inevitable pointless debate over whether Typhoon Haiyan or other extraordinary natural events are “caused” by global climate change misses the point; the fact is, storms are generally getting more powerful even as we continue to build our homes and office parks in harm’s way.

So Long Miami

This was brought home forcefully to the inhabitants of the Front Range, in Colorado, where I live, last month when a “100-year flood” hit Boulder and the surrounding towns, inundating Jamestown and Lyons and destroying many of the roads into the canyons below the Continental Divide.  Years of hot summers, moderate winters, and drought conditions have parched the forests of the Front Range, resulting in massive fires like the 2010 Four Mile Fire; and the burnt-over hillsides are unable to soak up or slow down torrential rains, which overwhelmed the area’s watersheds.

“In the past two decades, a quarter million people have moved into Colorado’s red zones – the parts of the state at risk for the most dangerous wildfires,” observed I-News, in an report titled Red Zone: Colorado’s Growing Wildfire Danger.  “Today, one of every four Colorado homes is in a red zone….”

The biggest red zone is South Florida, where hundreds of miles of low-lying coastal areas could be inundated by the end of the century by rising seas.  “At two to three feet,” of risen tides, “we start to lose everything,” Harold R. Wanless, the chairman of the geological sciences department at the University of Miami, told The New York Times in an alarming story on Miami’s future.

Sandy, Haiyan, the Australian brushfires, the Colorado flooding: all just foretastes.  We all live in the red zone now.


Under Dark Skies, New Jersey Eyes Transit Microgrid

— September 11, 2013

During Tropical Cyclone Sandy in October 2012, over 2.6 million electricity customers in New Jersey lost power and thousands continued to struggle without it for weeks.  The estimated costs from property damage were around $65 billion, second only to Hurricane Katrina in U.S. history.  The aftermath of the storm underscored the need for more reliable grid infrastructure technologies in vulnerable coastal communities.  Today, the U.S. Department of Energy and the state of New Jersey are partnering to deploy a microgrid in the repair of New Jersey Transit’s (NJT) northeastern corridor, to be called the NJ TransitGrid.

NJT is the third largest transportation system in America, with a daily ridership of nearly 900,000, and is one of the most important access points to New York City.  During Sandy, the NJT rail operations center was flooded by 8-feet of water, and more than 300 rail vehicles were damaged.  The loss of NJT during Sandy was devastating to relief and evacuation efforts; total estimated costs to NJT were $400 million, and as of June 2013, 119 rail vehicles are still awaiting repair.  The future NJ TransitGrid will ensure that trains keep running when the grid goes down by adding grid-independent generation capacity in excess of 50 MW.

Disaster Prone

Microgrids use local and distributed energy generation and storage assets to enable communities, campuses, and organizations to operate independently of the power grid..  The NJ TransitGrid is the first system of its kind deployed in a major civilian transit system.  The microgrid technologies and management systems to be used in New Jersey have been undergoing development and demonstrations by the military at major installations in Hawaii and Colorado.  It’s no coincidence that these technologies are gaining interest in communities vulnerable to natural disasters.

At this point, though, the NJ TransitGrid is just a concept with a $1 million budget from the federal government to plan over the next 5 to 6 months exactly how the system will work and what assets it will employ.  Department of Defense microgrid programs have used a variety of traditional energy generation assets like diesel generation sets, solar PV, and wind, along with some cutting-edge energy storage technologies like vehicle to grid (V2G)-enabled plug-in electric vehicles (PEVs).

The fact that the NJ TransitGrid will be deployed on a transit system presents opportunities to use the vehicles for energy storage and/or generation with advanced batteries.  Portions of NJT’s 2,000-plus buses can be converted to V2G-enabled PEVs, providing reserve power or balancing grid frequency when not in use, and batteries installed on the NJT’s light rail lines  can capture energy from braking trains.  These technologies are just emerging in demonstration projects and are, therefore, costly to implement.  However, increased adoption by the military and the major rail lines should drive those costs down, making microgrids attractive for communities vulnerable to natural disasters across the globe.


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