Schematic Design (35%)
The schematic design (35%) phase provides an opportunity for the Federal agency and design team to come together and ensure project goals established during programming, discussed during the design charrette, and refined during the preliminary design are represented in the design as it moves forward.
During schematic design, preliminary considerations for potential renewable energy technologies will be primarily based on fuel types available to the project (electricity, natural gas, district steam, etc.), expected project end uses, and overall project goals. Projects with any particular dominant fuel use may find a number of technologies are not feasible in meeting project goals. Feedback from the building energy simulation can be used in preliminary renewable energy system sizing and targeting strategies throughout the design process.
At this point of the design phase, changes are likely to occur as project design components are being refined or new ideas and opportunities are presented for consideration. While deviating from a particular renewable technology needed to meet project goals is not encouraged, changes made to specific technologies during the early stages of the design process allow changes to be integrated with less impact on the subsequent design phases.
The review of these schematic design documents by the integrated design team, including the project energy lead, allows an objective evaluation of the current design and can help ensure that it is on track to meet established project goals. Architectural features, mechanical system design components, and input from others disciplines can lead to design changes that may result in a particular renewable energy technology to be more effective than another in meeting these goals. Any changes should be continually updated and reflected in the energy model being used for the project.
- Results of the Renewable Energy Feasibility Study
- Energy Simulations: Schematic Design vs. Baseline
- Comparing Energy Efficiency and Renewable Energy Measures
Results of the Renewable Energy Feasibility Study
Schematic design is the appropriate time to get detailed information on renewable energy technology options from a renewable energy feasibility study. This study, which should be provided by the architectural and engineering (A&E) firm or their subcontractors, provides in-depth details on energy production, costs, savings and implementation issues associated with specific technology products.
Input from the feasibility study provides detailed reinforcement for the selection of the most effective set of renewable energy technologies for the building. Schematic design is the last opportunity to add any new technologies into consideration, so that information is needed at this point if the feasibility study highlights unexpected potential or concerns with any of the technologies.
Energy Simulations: Schematic Design vs. Baseline
Engineering calculations and whole building energy simulations should be reviewed for both current design and measures to further increase overall building efficiency. This iterative simulation and review process should occur in all phases of design.
When making energy saving comparisons, a number of ways exist to establish a baseline building and energy case for reference. For new construction projects, building energy simulation methodologies outlined in standards like ASHRAE 90.1 and ASHRAE 189.1 can be used. Publications like ASHRAE's Advanced Energy Design Guides provide guidance for achieving 50% energy savings beyond the minimum requirements of 90.1-2004.
When an existing building is to be renovated, the past energy consumption information of the building can be used. It is suggested that a baseline model incorporating existing design conditions be developed and calibrated to match the existing energy use within a reasonable range when evaluating reductions from the baseline.
Additionally, separate energy simulation files should be preserved at each phase of design that reflects the design documents at that point in time. Any changes that have been incorporated into the current model should be documented with the simulation files. Changes may include operating schedules, architectural components, mechanical system components, or other energy end use systems, including process loads, that may not have previously been identified.
For example, a facility that initially included a recreation space with showers and a tempered pool is changed to allow for more office spaces. Due to the high demand for hot water, a solar thermal system was initially chosen to meet the projects renewable goals. With this change characterized by a decrease in hot water demand and an increase in office equipment, it was determined that a photovoltaic system would work best for the project.
Simulations of the current design, along with other design options being considered, can provide critical information to the project as it progresses.
Comparing Energy Efficiency and Renewable Energy Measures
When evaluating design options to meet project energy goals, it is important to consider energy efficiency first in conjunction with potential cost impacts associated with either an increase or decrease in the required capacity of any renewable energy technology. In most cases, energy efficiency can be the most cost-effective option.
Because the renewable energy feasibility study provides specific cost information for a range of technologies, analysts can start to use a levelized cost of energy (LCOE) of renewable energy to determine the most cost-effective steps toward energy goals.
For a given measure, the associated net cost over the expected component life or determined performance period can be converted to a cost/unit energy saved over this time interval. A simple example, assuming constant energy prices and performance over this time interval described this as follows.
Considering electrical energy, an efficiency measure with a cost premium of $50,000 has been shown to save 30,000 kWh per year at a price of $0.10 per kWh. Evaluated over a 20-year period, assuming constant utility cost and component performance, the LCOE for this measure is $0.083 per kWh. The fact that the LCOE is less than the retail cost of energy suggests that this is a favorable measure. This scenario should be compared with any renewable energy system being considered when the total cost of the system is evaluated with the same considerations. Dependent on the project location, utility rates, and incentives for a particular technology, the LCOE for either measure should be compared and evaluated.
Other information, such as de-rating, discount rate, degradation, and maintenance, can be incorporated into LCOE analysis to provide considerations not addressed above. More information on LCOE and other financial evaluation is available from the EERE Office of Planning and Budget Analysis.