Distributed energy generation plays an important role in smart grid efficiency and sustainable building practice.  Distributed energy power plants, especially at the industrial and commercial levels,  help to mitigate the risk of "rolling blackouts" and other market rate fluctuations brought on by consumer reliance on centralized power plants.  Decreasing consumer reliance on these centralized plants benefits the overall energy system by addressing rising demand in a cost and time effective way.  Integration of storage and generation technologies with new and ongoing building projects allows for an increase in property market value while providing below market rate power on site.  The methods of creating power are as diverse as the industries that implement them.  Accurate evaluation of the available resource in a given area can allow for low impact, grid neutral, and even net positive situations where surplus power is sold back into the grid.  Often combinations of resource use is the most effective; combining the individual strengths of each resource and proportioning based on seasonal power consumption variations, cost and availability.  It is important that builders know the basics of resource evaluation and can plan and manage the most cost effective and energy positive solution for each unique building project.  Here we will discuss the basics of site evaluation inputs for the leading renewable power options: solar and wind.

Solar
The first green energy technology that comes to mind for most people, solar power continues to dominate the renewable energy market.  This majority market share stems from the relative ease of installation and the minimal aesthetic impact.  Solar is an ideal option for projects that have a large amount of roof space available, such as storage facilities and warehouses, etc.  The solar index at the site is the driving contributor to the power output calculations for these systems.  In addition to the solar index accounting for the tilt of the earth relative to the latitude, it also creates a geometric situation that impacts the angle of panel installation for efficiency.  Also, the shadows cast from surrounding objects must be accounted for, as well as how these areas change over the course of a year to efficiently evaluate and size a site.  With the correct data solar collectors are fairly easy components to size, install, and begin generating power.

Wind
Small wind units, typically on 50' towers, have been the most extensively installed product in the wind industry for many years.  Their use in residential and small industrial energy generation stems from their easy to manage installations and grid interfacing.  It is important to realize that these systems are sized by their rated outputs, such as a 5kW device.  This output is never maintained due to the inconsistent nature of wind itself, and it is very important to realize this and plan accordingly.  Studying the wind resource and the variations between times of day and seasons in the year will allow for the most efficient development plan.  This data collection and analysis also allows more accurate product sizing for use in direct applications, such as powering a well pump, etc.

This graph shows an example of the data measured in planning a wind installation.  The velocity profile changes over the course of the day and year in a quantifiable way given the right data sets.  The combination of many data sets over the year can result in accurate estimations of the projected power output for a given site and, in turn, a targeted way to optimize resource capture.  As with solar, the collection and interpretation of the data for the respective site is crucial to optimizing system performance.  Once this research is complete however, the systems start making power and the unit begins paying off the initial investment.

Energy Storage
One downside to these technologies is fairly obvious: it isn't always sunny and it isn't always windy.  To address this reality another aspect of distributed energy is being developed: storage of the surplus energy produced for use when the resource is scarce.  These systems use a wide range of technologies to accomplish their task; from chemistry in batteries to physics in flywheels.  These devices are created near concentrations of consumers to charge while demand is low and feed that power back to the grid when demand rises, which is often in the evening when everyone gets home from work to turn on the TV, open the fridge, and crank up the heater or AC.  The flywheel is an ideal solution from a sustainability perspective as it requires only a very heavy and large disk to be spun, converting the electrical power potential into mechanical momentum.  If one doesn't account for the motor to spin it, a flywheel can be essentially "recharged" an infinite amount of times.

Summary
Centralized power has been the power generation strategy in the U.S. for years.  The downsides to this system are many: a single point of failure can result in power loss over large areas, the upfront cost of construction and the associated time lines creates a sizable lag between investment and return or production, and centralized power systems require "peak plants" which have extremely high operating cost generators for use only when demand spikes.  Through the use of distributed power generation and smart grid monitoring and control systems a single point of failure can be mitigated by power supply generation through the customer base.  This decreases volatility found in the energy market and allows for increased returns when used with other green building techniques.  Also, the use of these smaller distributed systems allows for relatively fast construction and installation, lowering the time of return on investment and mitigating the risk of construction delays.  As with many complex problems, there is no cure all solution to rising energy demand.  It will take a combination of the available resources, generation technologies, energy storage technologies, as well as the many other sustainable building practices to boost our economy while lowering our dependence on finite resources.  Distributed energy systems are sure to play a crucial role as we move down the path toward a future of sustainability and stable energy costs.

Phillip Mathews
Product Development Engineer - Renewable Energy Consulting
design@prevailingwindtech.com
Santa Barbara CA 93105
UCSB