Load Matching, Grid Interaction, and Advanced Control - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 296

while maintaining voltage and frequency requirements. Load management
is a problem that is present at different scales (e.g., national grids, regional
grids, and distribution networks).
In contrast with the utility grid, load management and peak load reduction
have received somewhat less attention in buildings. Buildings have been
largely considered as passive consumers that take energy from the grid or
other energy carriers to supply their own needs as they appear. When peak
load reductions are achieved, it is often not the result of a deliberate effort,
but the by-product of energy efficiency measures (e.g., adding insulation
results both in less energy use and smaller peaks). Regardless of the
meteringpointorenergycarrierconsidered, annual energyusehasbeenthe
yardstick traditionally used when describing the performance of a building.
Peak load prevention adds an additional element of complexity to the task
of maintaining a comfortable temperature while fulfilling all the other
functions required in a building, such as communications, lighting and
waste disposal.
A building designer or operator has at least two important reasons for
aiming to reduce peak loads:
• Utility savings . Depending on the tariff structure in place, reducing
peak loads can offer significant savings in utility bills. In the case of
commercial buildings, utilities and DSOs apply rate structures that
heavily penalize energy use during peak hours, via demand charges or
time-of-use (TOU) rates. In these buildings, a combination of
technologies and heuristic operational strategies are used to reduce
peak loads. Traditionally, flat rates have often been applied to
residential customers, and as a result, home owners tend to be less
concerned about peak-shedding measures. However, this situation is
rapidly changing, and time-of-use rates may soon become more
widespread even in residential buildings.
• Equipment size reductions . Lower cooling and heating peak loads
allows for the use of smaller (i.e., lower rating) installed equipment. The
customary practice today, recommended by professional organizations
(ASHRAE, 2005), is the installation of mechanical equipment sized to
match peak cooling or heating loads. These loads can effectively be
reduced by incorporating more thermal mass in the building itself
(Braun, 1990) or by adding thermal inertia as part of the building
technical systems. The use of thermal energy storage (TES) devices