|
Overview
Cooling energy use is second only to lighting energy use in commercial buildings. Cooling in commercial buildings accounts
for 14% of California's peak electrical demand. Both energy consumption and peak demand are increasing, particularly in the
state's hotter inland areas. Cooling system efficiency can be improved through the use of compressorless cooling
technologies, specific techniques for cooling occupied spaces effectively, and reduction of distribution system losses.
Low-energy cooling systems employ a number of different technologies. Common characteristics are that these systems:
- Dissipate heat from the interior of the building to the environment directly without any kind of refrigeration cycle
(e.g., natural ventilation, evaporative cooling);
- Cool occupied spaces using particularly effective techniques (e.g., displacement ventilation or radiant cooling
so that the air or water used to cool the space doesn't have to be as cold as is traditionally required; this approach makes
it easier to dissipate heat directly to the environment);
- Distribute cooling to the different parts of the building effectively, either by using water instead of air or by
sealing and insulating ducts so that less cooling is wasted before it gets to where it is needed.
The main goal of the Low-Energy Cooling Element is to significantly reduce the energy consumption and peak demand associated
with the cooling of commercial buildings. Additional project goals are to improve health and productivity through the use of
space-conditioning systems that can reduce energy consumption while improving indoor air quality (e.g. displacement
ventilation, evaporative cooling) or improving comfort (e.g. chilled ceilings).
|
- Technical Highlights
|
 |
The objectives of the project are to identify and evaluate appropriate combinations of low- energy cooling technologies, including
efficient distribution systems, and to develop the simulation models required both for this evaluation and for the design of such
systems for individual buildings.
Low Energy Cooling Brochures:
This project is using computer simulations to identify potentially synergistic combinations of existing compressorless cooling
technologies, energy-efficient methods of cooling spaces, and energy-efficient distribution systems. The energy savings potential
of the low-energy cooling system combinations are being assessed for the 16 California climate zones and a range of building types
(high/low mass, high/ low internal gains, high/medium/low solar gains).
Tasks:
Phase I of the project involves assessing cooling systems that can be modeled using the DOE-2.1E whole-building energy
simulation program.
In Phase II, EnergyPlus, the U.S. Department of Energy's replacement for DOE-2, will be used to model a wider range of cooling
systems, including those for which models are currently being developed in Project 2.3. This activity is scheduled for the third
year of the program.
Commercial duct performance work is being conducted in order to follow through on the strategy outlined in the Public Interest
Energy Research (PIER) transition project final report for incorporating duct performance into the Title 24 compliance procedure.
That strategy involves producing a complete package for including duct leakage (and other duct performance factors if it is
practical to do so) in the next update of the Title 24 Energy Efficiency Standards for Non-Residential Buildings.
Tasks:
Examine recent work on whole-building modeling of duct leakage and insulation energy impacts in light and large commercial buildings
and determine which aspects we can carry over to Title 24 compliance processes for large commercial buildings. Based on this review,
develop a duct analysis methodology to be used for benefits analyses in support of the 2008 Title 24 Standards (with recommendations
on how to proceed over the long term using EnergyPlus or DOE-2).
Using the simulation approach identified in Task 2.2.1, assess the benefits of duct leakage and insulation improvements in support
of the 2008 Title 24 Standards.
Recommend a set of changes for the 2008 Title 24 Standards to incorporate duct efficiency metrics and make use of the new duct
modeling capabilities.
Develop a proposal to revise the Alternative Calculation Method (ACM) to include an overall metric for distribution system
efficiency in the reporting requirements of the 2005 Title 24 Standards. The proposed metric is the ratio between the energy
expended to transport heating, cooling, and ventilation throughout a building and the total thermal energy delivered to the
conditioned zones in the building.
DOE's new building energy simulation program EnergyPlus will be extended with models to predict the energy performance of low
energy cooling systems. EnergyPlus will also be extended to treat duct system performance in order to support the assessment
of the benefits of reduced duct leakage and increased thermal insulation to be performed in Project 2.
Tasks:
Extend EnergyPlus with a model to predict the energy performance of Displacement Ventilation systems.
Extend EnergyPlus with a model to predict the performance of Natural Ventilation systems.
Extend EnergyPlus with a model to predict the energy performance of Cool Ceiling Panel systems. The radiant cooling model will
be developed based on the extended slab model currently in EnergyPlus.
Contact:
Philip Haves,
Lawrence Berkeley National Laboratory (LBNL), (510) 486-6512
|
