Tag Archives: thermal energy storage

Is the Future of CSP Dim?

Concentrated solar power (CSP) is an often overlooked method to generate electricity from the sun. As the name implies, CSP systems concentrate the sun’s energy, and do so with the use of reflective mirror surfaces. In commercial CSP plants, the concentrated sunlight is typically used to heat a working fluid which in turn generates steam to produce electricity via a steam turbine. Although commercial CSP plants have existed since the 1980s, a number of factors have hindered the technology’s penetration into the energy market. What are the factors holding this technology back? And (perhaps more importantly) is there any hope for the technology to grow in to a competitive source of electricity?

In recent times, photovoltaic (PV) prices have dropped dramatically, leading to a strong interest in installing utility-scale PV. This has also had the secondary effect of reducing the investment in CSP, since it is currently a more expensive method to generate electricity from the sun. Because of cost, investors have opted for PV over CSP – so much so that many planned CSP plants are instead being converted to utility-scale PV plants. Environmental factors have also had an effect. Last year, BrightSource Energy’s planned 500-megawatt CSP plant encountered an obstacle after surveyors discovered fossil deposits on the planned building site. Further concerns on the site’s impact on wildlife, as well as the cost of the plant forced BrightSource to put the project on hold.

However, CSP does have marked advantages over other forms of renewable energy. Of particular interest are the methods with which CSP can overcome intermittency problems. Power plants which combine CSP and traditional primary sources of energy can provide electricity day and night. Integrated thermal storage seeks to overcome this problem as well – the working fluid which drives the CSP plants can be stored in tanks and then utilized at a later time to generate electricity at night or during periods of low sunlight. This provides a greater flexibility to the grid than PV and wind typically provide. Recent studies back up this claim, showing that thermal storage adds a market value of up to $14/MWh, and a capacity value of up to $30.50/MWh.

Domestically, companies such as SolarReserve has taken advantage of thermal storage, and have projects underway which will prove the technology’s viability. Furthermore, the largest solar thermal energy generating facility in the world operates on both solar and natural gas and powers over 200,000 homes according to NextEra Energy Resources, the company that owns the facility. 

In total, over 1.4 GW of CSP plants were under construction in the US last year. Once operational, these projects will help to demonstrate the feasibility of CSP in the US. This information, coupled with the success of overseas companies (see Abengoa) and projects (such as in Abu Dhabi, Spain, etc.) will ultimately show the viability of CSP in the coming years. Therefore, although there is definitely hope for the technology to grow, its success will ultimately rely on the ability to drive prices down through methods such as thermal storage. Only then, it seems, will investors be more willing to add a greater share of CSP into the renewable energy sector.

(additional references linked in article)



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Thermal Energy Storage and the Benefits of Distributed Power Storage

As the total electricity consumption in the US is projected to continue rising, innovative use of technology can more efficiently use the existing generation capacity to meet this increase in consumption without having to build additional power plants, by shifting the peak demand of electricity usage.  In effect, level out the load curve by shifting the consumption of electricity from peak hours (i.e., during the day) to off-peak hours (i.e., during the night). 

A large percentage of peak demand is generated by the summer time use of residential air conditioners.  Residential air conditioning accounts for the largest percentage of total electricity consumed in the home, approximately 16.0%[1].  During hot summer days, meeting the electricity demands from residential air conditioners can be problematic for utilities, which may be required to build additional power plants just ensure that the electricity demanded at peak hours during a couple of the hottest summer days can be met.

This is where the use of innovative technology, such as thermal energy storage, can shift the timing (peak hours to off-peak hours) of electricity usage from air conditioners and thereby reduce the need to expand generation capacity.  A company called Ice Energy is attempting to do exactly that, by using ice. Ice Energy recently signed a contract with Southern California Public Power Authority to provide 53 MW of storage in the form of rooftop air conditioner units that use off-peak electricity to make ice that is then used during the day to provide the cooling[2].  These units thereby reduce the electricity required during peak demand by relying on the ice instead of an electric compressor to cool the air. 

The use of these types of thermal energy storage systems can be considered a type of distributed energy storage because they are located at the load instead of the source.  This can have several advantages over a centralized power source (e.g., a gas peaking power plant) in that they require no additional infrastructure, no permitting or siting requirements, and they only require electricity that is already available.      

As the US grabbles with how to satisfy increasing energy consumption, deal with potential climate legislation, and meet the rising cost of energy production (the current price for a 300MW coal-fired power plant is about $1 billion[3]) the use of distributed energy storage systems could help address all of these challenges, at least partially. 

[1] http://www.eia.doe.gov/emeu/recs/recs2001/enduse2001/enduse2001.html

 [2] http://greeninc.blogs.nytimes.com/2010/01/27/storing-energy-as-ice/?scp=3&sq=energy&st=cse

 [3] http://www.jsonline.com/business/29482814.html


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