Modeling Tool for Efficiently Co-Locating Multiple Means of Generating Electricity from Renewable Energy Sources
by Thomas Manaugh, PhD, and Saïd Majdi, M.S.
A vast majority of scientists believe that global warming is a real phenomenon and that it is caused at least in part by accumulation of greenhouse gases when fossil fuels are burned for energy. Many scientists fear that certain tipping points have been reached or will soon be reached that will make it nearly impossible to halt rapid global warming’s catastrophic effects — including loss of species, increasingly frequent extreme weather events, droughts, floods, crop failures, famines, and rising seas.
An invention, “System for Generating Electricity from Alternative Energy Sources Located on a Floating Platform,” has been granted patent #8,097,218 by the USPTO (Manaugh, January 17, 2012). The patent discloses a floating platform, called Energy Island, which generates electricity from hydropower and other renewable resources of energy (1).
The main claim of the patent is for a system that generates electricity from hydropower, as stated in Claim 1: “A system for generating electricity, the system comprising: a platform capable of floating on a body of water, the platform having a top panel, a first side panel, a second side panel, and a bottom panel that restrict water flow through a narrowing duct formed by the panels as the water flows under the top panel and exits a widening duct formed by the panels; a plurality of energy modules, wherein each energy module produces electricity from a differing source of energy for storage and distribution and is affixed to the platform; wherein one of the plurality of modules is a module employing at least one water-driven turbine that generates electricity when a current of water flows through the duct located below the top panel of the platform, thereby causing the turbine to turn and produce electricity.” Dependent on that main claim are additional claims for means to generate electricity from wind, waves, differences in temperature between layers of water, and solar radiation.
New Technologies for Co-Locating Means of Generating Electricity
The patent for Energy Island was granted for its innovative design of an efficient hydropower system to generate electricity from a floating platform. Other recent technologies offer opportunities for the Energy Island platform to generate electricity in new and cost-effective ways.
The top surface area of Energy Island will be extensive in order to enjoy economies of scale. Even so, the area available for installation of solar panels, wind turbines, and other devices will be limited. Thus, for optimizing the design of Energy Island, it will be important to identify types and configurations of installed equipment efficiently to generate the most amount of electricity per unit of surface area.
A group of researchers at MIT recently published results of an attempt to improve capture of solar energy (2). By stacking solar cells in a unique way, Bernardi et al found they could capture as much as 20 times more the energy in a given area as would be captured by conventionally deployed cells in the same area.
Research by Dibiri at Caltech (3) has shown a ten-fold advantage in per-surface-area generation of electricity when tightly grouped vertical-axis wind turbines are used instead of conventional horizontal-axis turbines, which cannot be tightly grouped.
Thus, opportunities for cost-effective generation of electricity for a given surface area are suggested by (a) Manaugh with respect to an innovative design for co-location, (b) Bernardi et al with respect to increasing yields from solar cells and (c) Dabiri with respect to increasing yields from wind turbines.
Goals and Need for Research
Generating cheaper and more reliable electricity by co-locating means of tapping renewable energy and employing economies of scale is a worthwhile goal, but realizing that goal will require identifying optimal configurations of equipment to take best advantage of variable environmental conditions of sun, wind, water, and temperature. Any optimal configuration would be a system of systems that would be affected by input from many variables.
Research is needed to develop a mathematical modeling tool so many variables can be iteratively manipulated to arrive at optimal configurations of multiple equipment types across a number of environmental conditions. Of special interest is how applying formal optimization techniques can lead to environmentally friendly utilization of presently underutilized resources.
Is this a feasible approach to a problem identifying cost-effective means to generate electricity from renewable resources? A positive answer to that question is supported by prior examples of finding and optimizing practical solutions to familiar problems.
One relatively simple and familiar example of how analysis, modeling, and optimization can significantly increase efficiencies and safety is seen when a new HOV lane is planned for co-location with general-purpose lanes of travel on a highway. Analysis might show (a) existing congestion on the highway that decreases work productivity and aggravates and frustrates commuters, (b) many vehicles with multiple occupants already present on the highway, and (c) existing popular share-a-ride or park-and-ride programs. Using those and other variables, a mathematical model could be constructed to predict beneficial effects of adding a new HOV lane with various features of length, location, and times of operation. Optimization could then pinpoint how long an HOV lane should be, where its entrance and exit should be located, and how its use should be regulated. That kind of careful implementation is likely to have transformative results for commuters and the environment: quicker and less stressful commutes, fewer traffic accidents, reduced consumption of fossil fuels, less air pollution, and less wear and tear on vehicles.
Just like it is important that we optimize our transportation systems, it is also important that advances in the development of alternative energy should help solve the crucial problem of global warming. That is the motivation and rationale for the present request for funding to develop a mathematical modeling tool that can be used to predict costs and identify savings from optimal co-location of multiple technologies for converting renewable energy to electricity.
System engineering methodology will be used to perform an analysis of Energy Island’s integrated renewable energy system to make a performance assessment based on its constituent subsystems and the overall system architecture. System engineering methodology, as well as modeling and optimization techniques, offer tools to determine the optimal configuration of the integrated renewable energy system with its mix of renewable energy technologies. This is an important problem that, though complex and far from trivial, can be solved.
Parameters that provide input to the optimization process will be identified by analysis. These input parameters can be site-specific; e.g., wind speed, ocean current speed and solar radiation intensity. They can also be technology-specific; e.g., device size and efficiency. In addition, constraints such as the Energy Island dimensions and critical costs will govern the optimization process.
After analysis, a cost-effective software tool will be chosen to solve the optimization problem associated with implementation of the integrated renewable energy system called Energy Island. Software tools, such as IBM’s ILOG CPLEX Optimizer, for example, offer functionality that is especially suitable for this type of optimization problem. These kinds of software tools have been used in many industries, including energy and utilities, to improve efficiency and reduce costs.
When the optimization process is complete, the optimal solution will be identified, i.e., the most cost-efficient implementation of the integrated renewable energy system.
General guidelines will be identified for any integrated renewable energy system to provide optimal yield, given specific local operating conditions for each of the energy sources. For example, determining the portion of available surface area to allocate to each of the energy technologies is critical to the successful deployment of any integrated renewable energy system, but portions will vary under differing environmental conditions.
In brief, here are the tasks that will be performed:
- Determine the benefits and possible cost-savings of co-locating renewable energy technologies
- Provide a clear understanding of where optimization fits into the problem of co-location of renewable energy technologies
- Formulate criterion/criteria for optimization
- Select an appropriate optimization strategy
- Solve the problem using formal optimization techniques
- Evaluate optimization results
- Formulate general design guidelines for implementing optimal solutions
Though the proposed tool would be useful in designing an Energy Island, it is a goal that the tool would be useful in optimally designing any system where multiple sources of renewable energy would be co-located to generate electricity.
One goal of the U.S. Department of Energy is to find innovative ways hydropower can be used to generate electricity at a levelized cost of under 6 cents per kWh. Hydropower is the main source of renewable energy that will be the focus of the research proposed here. The research will identify optimally cost-effective ways that hydropower and other sources of power can be combined at a single location. Below is a specific example of how co-location of hydropower equipment could be advantageously included in a practical project involving generation of electricity from renewable energy.
A report on a new project is titled “Construction of Japan’s largest solar power plant to begin in July at a cost of ¥25 billion” (4). The project involves placing 290,000 solar modules on a floating platform in the ocean near the city of Kagoshima. The solar energy project will cost $309 million and produce 79,000MWh annually, enough electricity to power 22,000 households.
It can be assumed with assurance that the Japanese installation has been designed so that it will be capable of transmitting electricity that is generated during a time of the year when generation of electricity from solar radiation is at a maximum. Maximal generation will probably be found to occur on a clear summer day when the sun is approximately at its zenith.
Thus, it is logical there will be much unused transmission capacity during the rest of the year — most notably during nighttime but also during overcast days. Only a small fraction of total transmission capacity will be used. The floating platform and its associated transmission equipment will be completely unproductive most of the time if some kind of co-located electricity-generating equipment is not used.
It is hypothesized that under some scenarios hydropower equipment, located under and affixed to the floating platform, could be used to intercept tidal currents and convert energy of the currents into electricity. If that equipment were to operate during times when the platform and its transmission equipment would otherwise be unproductive, the hydropower equipment could create electricity at a low marginal cost. That is, the equipment could take advantage of existing but under-utilized infrastructure and transmission capacity to provide low-cost electricity.
It is specifically hypothesized that optimizing the design of co-located electricity-generating equipment will result in identifying at least one scenario under which hydropower could be efficiently converted into electricity at a marginal cost of under 6 cents per kWh. That such a hypothesis could be proven is obviously important because that result could inform the design of projects, like the one in Japan, costing hundreds of millions of dollars. That would be transformative.
- “System for Generating Electricity from Alternative Energy Sources Located on a Floating Platform” by Thomas Manaugh, retrieved from the Internet, January 31, 2012, at http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2&f=G&l=50&co1=AND&d=PTXT&s1=manaugh.INNM.&OS=IN/manaugh&RS=IN/manaugh
- “Potential Order-of-Magnitude Enhancement of Wind Farm Power Density via Counter-Rotating Vertical-Axis Wind Turbine Arrays” by John O, Dabiri, in Journal of Renewable and Sustainable Energy / Volume 3 / Issue 4, retrieved from the Internet, January 31, 2012, at http://jrse.aip.org/resource/1/jrsebh/v3/i4/p043104_s1?view=fulltext
3. “Solar energy generation in three dimensions” by Marco Bernardi , Nicola Ferralis , Jin H. Wan , Rachelle Villalon and Jeffrey C. Grossman in
Energy Environ. Sci., 2012, Advance Article retrieved from the Internet, April 24, 2012, at http://pubs.rsc.org/en/content/articlelanding/2012/ee/c2ee21170j.
4. “Construction of Japan’s largest solar power plant to begin in July at a cost of ¥25 billion” by Dante D’Orazio, retrieved from the Internet at http://www.theverge.com/2012/4/10/2939187/japan-largest-solar-power-field-kyocera-construction on April 25, 2012.