<p><strong>Create an emergency load profile</strong></p>
<p>The tool offers three different ways to estimate the hourly electricity profile during a disaster event, depending on which data are available to the user. The tool uses this information to create an hourly emergency load profile for a full year.</p>
<p style="padding-left: 30px;">• <strong>Quick</strong> The user inputs the annual electricity peak demand of the building (typically found on the electricity bills), the location of the building (by clicking on the climate zone map), and percentage of the total electrical load that the user wants to support during a disaster event. The tool creates an hourly emergency load profile based on an electrical load profile for a typical office building in the chosen climate zone, scaled to match the entered peak demand and desired load percentage. The default profiles are modeled load data representing the <a title="DOE reference buildings" href="http://energy.gov/eere/buildings/commercial-reference-buildings" target="_blank">Department of Energy’s large office reference building</a> for more information. Other building types are not modeled; however, this option allows a quick sizing estimation only.</p>
<p style="padding-left: 30px;">• <strong>Standard</strong> The user uploads the actual electricity profile for the building. This data must contain hourly or 15-minute data for a full year, starting at midnight on January 1, to match the hourly PV data used in the calculations. All of the data must be in column A, and there must be no other data in the file, such as dates and times. The user also enters the percentage of the total electrical load that the user wants to support during a disaster event. The tool creates an hourly emergency load profile by multiplying the uploaded electricity data with the emergency load percentage.</p>
<p style="padding-left: 30px;">• <strong>Detailed</strong> This is the most accurate method. The user enters the following information about each load type that will be running during a disaster event:</p>
<p style="padding-left: 60px;">• Wattage per fixture/appliance/device</p>
<p style="padding-left: 60px;">• Quantity</p>
<p style="padding-left: 60px;">• Daily schedule (start and stop hours)</p>
<p style="padding-left: 60px;">• Annual schedule (start and stop months)</p>
<p style="padding-left: 60px;">• % run time (% of the time each fixture/appliance is used)</p>
<p><br /><strong>PV generation data</strong></p>
<p>The PVWatts Calculator provides estimated PV electricity generation for different locations throughout the United States. The user inputs information about the location of the building (city, state, zipcode), which is used in the PVWatts Calculator to access hourly output data for 1 kW AC of installed PV array for that specific location. </p>
<p>The output is based on the PVWatts Calculator default settings for module type, array type, tilt, azimuth, system losses, and inverter efficiency, but the advanced inputs section allows the user to adjust these settings.</p>
<p><br /><strong>Design scenario selection</strong></p>
<p>The sizing calculations are performed for every hour of the year and the design outage start hour and system capacities are determined based on the chosen design scenario (Typical or Worst):</p>
<p style="padding-left: 30px;">• <strong>Typical</strong> (default setting) represents the average outage hours of the year. The PV and battery systems are sized to provide desired resilience with a probability of at least 50%.</p>
<p style="padding-left: 30px;">• <strong>Worst</strong> represents the worst outage hours of the year in terms of largest required system capacity. The PV and battery systems are sized to provide desired resilience with a probability of 95 to 96%.</p>
<p><br /><strong>Existing on-site power generation</strong></p>
<p>The advanced inputs section gives the user the option to include any existing PV arrays and backup diesel generators.</p>
<p><br /><strong>Existing PV array</strong></p>
<p>An existing PV system will reduce the additional PV capacity required for desired resilience. The tool assumes the same power output for the existing PV array as for the new, and simply subtracts the existing capacity from the total PV capacity to calculate the additional PV capacity needed.</p>
<p>If no additional PV capacity is desired, the user can check "Don't add additional PV". The tool will then calculate the battery capacity required to meet desired resilience for the specified existing PV array.</p>
<p><br /><strong>Existing diesel generator</strong></p>
<p>Some buildings (for example police and fire stations) might have emergency diesel generators. If that is the case, it is possible for the user to include the generator output in the calculations and thereby reduce the PV capacity required for desired resilience. <br />The user enters the rated capacity and the available fuel storage, and the tool calculates the hourly output based on following assumptions:</p>
<p style="padding-left: 30px;">• The generator runs every hour that the PV output is less than 30% of its rated capacity (based on evaluation of different scenarios)</p>
<p style="padding-left: 30px;">• The diesel tank is assumed to be empty by the end of the chosen target duration</p>
<p style="padding-left: 30px;">• The generator output is constant over the hours it is operating and any excess generation will be used to charge the batteries</p>
<p style="padding-left: 30px;">• The efficiency varies with load, according to Cummins Pacific’s - Diesel Fuel Consumption Rate Calculator</p>
<p><br /><strong>PV array sizing</strong></p>
<p>The PV system is sized to generate enough electricity (in kWh) to cover the net energy demand (emergency load minus any diesel generator or existing PV array output) during the target outage duration and any conversion losses in the solar+storage system.</p>
<p>The PV capacity (in kW) required is calculated using the PVWatts generation data for 1 kW of PV for the desired target outage duration during the design outage hours.</p>
<p><br /><strong>Battery system sizing</strong></p>
<p>To make the most use of the battery system, it should also be used during non-emergency mode. The chosen grid service (see the Assumptions tab) affects the risk of the batteries being discharged when a power outage strikes. To account for the worst case scenario in the system sizing calculations, the tool assumes the batteries to be at their lowest level typical for each grid service, which means that extra capacity needs to be added to compensate for this risk.</p>
<p>The battery system is sized based on four criteria:</p>
<p style="padding-left: 30px;">• Discharge rate (in kW) required to meet the net load for every hour during the outage</p>
<p style="padding-left: 30px;">• Charge rate (in kW) required to capture any excess PV output for every hour during the outage</p>
<p style="padding-left: 30px;">• Discharge capacity (in kWh) required to provide enough energy during the hours with a positive net load during the outage - extra capacity is added to compensate for the risk of the batteries being discharged at the start of the outage</p>
<p style="padding-left: 30px;">• Charge capacity (in kWh) required to capture all excess energy during the hours with an excess PV output during the outage</p>
<p><br /><strong>System duration probability</strong></p>
<p>The probability that the calculated system will provide desired resilience (i.e. support the emergency load) varies depending on when the disaster strikes. The variations are due to seasonal and daily changes in load and PV output, as well as chosen grid service. To determine whether the proposed system provides desired resilience, the system duration for an outage happening every hour of the year is calculated. The probability of providing resilience for a certain number of days is presented in the bar chart.</p>
