Making Solar Inverters Smarter
The regulatory regime under which solar power is integrated into the grid is a moving target. Many moving targets, in fact, because states will exert as much or more control over rules and regulations as the federal government.
This long evolution is as important to energy managers and facility managers as it is to the utilities. The days in which solar energy was a minuscule percentage of the energy utilized are passing. Its dramatic growth is bringing these issues to the fore.
Currently, homes and businesses are allowed to freely send the electricity they generate but don’t use back to the grid. Their bills are credited. The utility industry maintains that this is an untenable model because the amount of energy and the timing of its entry into the grid is not under its control. This can play havoc both with its financial structure. “The utility has no visibility into what’s going on at the customer premise,” said Stewart Kantor, the CEO of Full Spectrum. “If a company generates solar or renewables, there is no visibility other than the billing aspect.”
The rise of renewables presents a second problem that must be addressed. The IEEE Spectrum this week posted a story discussing the dangers of the proliferation of solar power. Today’s systems are programmed to disengage from the grid if there is a problem. If that is done en masse, the grid can become destabilized. What started as a small problem can become much more serious. Thus, the growth of renewables on the grid, using current technology, adds energy – but threatens reliability.
The key to addressing both the cost and reliability issues, ironically, is a piece of equipment that is under the control of the end user, not the utility. The basic role of an inverter is to transform the direct current generated by a solar panel into the alternating current used by the grid.
In the past, inverters were “dumb” conduits. This was fine when solar was a boutique source of power. It no longer is. Enter the smart inverter. Solar Power World offers the basics. Smart inverters let the utility control the flow of electricity. Thus, as regulations change, smart inverters will give the utility the ability to accept, reject or otherwise control solar or wind power energy being returned to the grid. It will provide them with precise information about what is being sent upstream by homes and businesses. This, combined with emerging storage capabilities, can take pressure off the utilities.
The new devices can play a second role in maintaining stability. The new technology can keep a small problem from triggering a cascading series of automatic disengagements that will endanger the system:
But newer “smart” inverters can prevent a PV system from going off-line when it doesn’t have to. By doing so, they can actually make the grid more stable, by preventing the sudden deterioration of voltage and frequency that would otherwise occur when hundreds or thousands of PV panels are suddenly taken off-line, according to recent research by NREL and its partners.
Smart inverters are being made and the infrastructure around them being created. Full Spectrum has contributed intellectual property to an effort by the Institute of Electrical and Electronics Engineers (IEEE) – the organization behind WiFi standards — to create 802.16s, a wireless standard that will enable communications between the smart inverters and the utilities.
Much of the story on the integration of solar power into the grid has yet to be written. Energy and facility managers need to keep abreast of developments, of course. More specifically, they must make sure than the inverters that they buy either are smart or can be upgraded to that status when the time comes.
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