Load Matching, Grid Interaction, and Advanced Control - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 295

Distributed peak power generation is another issue that will become
progressively important (maybe even more so) than peak demand. With
increasingly higher penetration rates of building-integrated photovoltaics
and other distributed energy generation resources, utility grids will have to
accommodate power flows in the “opposite” direction with an infrastructure
(transformers, breakers, etc.) that has not been designed for this mode of
operation.
The electric grid was built in a hierarchical way, in which energy flows
from power plants through transmission lines, and then to the distribution
networks that deliver the power to the customers. Along this way,
transformers change voltage levels. Distribution system operators (DSOs)
must deliver electric power to the customers at the distribution level with
performance indices within certain limits (e.g., voltage). The layout of
distribution grids and the sizing of cables and transformers are carefully
planned in order to comply with these parameters.
At low penetration rates, the effect of distributed generation might be
beneficial,forexamplebyhelpingtomaintainvoltagelevels.However,some
problems are likely to appear in distribution grids with high penetration
rates, including power quality issues (overvoltage, harmonic distortion),
overloadingofcomponents,andincreasedlocallosses(Katiraei,Mauch,and
Dignard-Bailey, 2007). The concept of hosting capacity (loosely defined as
the amount of distributed generation that can be safely handled by the grid)
has been introduced (Bollen and Hassan, 2011). Grid-interaction indicators
will be critical to adequately characterize and manage bidirectional energy
flows.
6.1.2.2 Load Management in the Grid and Buildings
Load management has traditionally been an important issue for the utility
grid. Higher peak loads imply starting “peaking” power plants, which are
often more expensive, inefficient and polluting. In the electricity spot
market, the cost of electricity is higher during peak hours. A utility may be
forced to buy electricity from neighboring jurisdictions at very high cost. In
thelongrun,increasingpeakloadswillleadtotheconstructionofadditional
power plants as well as transmission and distribution infrastructures, with
the associated economic and environmental cost. At shorter time scales,
highly fluctuating loads complicate the already challenging problem of
matching the customers' needs with the power supplied from power plants