Codes and standards are required to help keep us safe along with the people who could use the product we design. Standards are there to maintain consistency between products and ensure that consumers are getting items that meet their expectations for reliability and safety. Codes and standards range from things that pertain to individual parts in a system to system-wide operation. Some codes and standards apply to the installation, maintenance, fire protocol, and system testing. For the design of our energy storage system, we focused on codes and standards that involve the testing and design of our subsystems. We can focus on the testing standard for our design since the parts we buy from companies have to meet their production standards before they can be sold to the public. For example, pressure vessels that have a capacity of over 15 psi have an ASME standard that they adhere to for proper testing and construction when they are first constructed. This also applies to any commercial pipes and fittings that are bought. In our testing, we did not need to follow this type of standard since we did not modify our pressure vessel. We are following the ASME Power Test Code 53 Mechanical and Thermal Energy Storage Systems (AME PTC 53-2018). This set of codes is still currently a draft, but they outline testing procedures for mechanical and thermal energy storage systems. The testing procedure describes putting a test boundary around the energy storage system to calculate power, energy, and efficiency. The figure below shows the setup for a generic test on an energy storage system.
Figure 1: Test Boundary Around Storage System
To conduct testing, we followed sections 3-2 to 3-5 in this test code collection to help push us in the right direction. Section 3-2 focused on creating a test plan to follow as we conducted testing. It mentions how it should “include the schedule of test activities, designation and description of responsibilities of the test team, test procedures, and report of results” and gave key elements of each of these, which we followed during testing of each subsystem and the overall system as long as it fit within the context and scope of our project. Section 3-3 involved the test preparations needed, which focused on elements such as the apparatus, instrumentation, and data collection. This was important for us to consider, since we needed to make sure to inspect the equipment before testing at all times, have proper instrumentation for data acquisition so that our analysis most accurately represented our system (such as thermocouples and pressure transducers or power readers for collecting the input and output power), and collect a high enough frequency of data to be able to accurately analyze our system (i.e collecting the temperature and pressure values every 30 seconds when testing our full system). Section 3-4 was vital due to its information on experimental set-up and procedures. This section gave key direction in helping us understand the importance of conducting preliminary testing (which we did when making sure our pressure vessel filled up and discharged at a reasonable rate with reasonable data values) and our modes of operation during the testing fit in line with our project goals. Finally, section 3-5 gave direction on data analysis and reporting of data; this was particularly important as some of our instrumentation readings were inaccurate when testing the temperature and pressure readings of our full system, which led to us having to reject those readings.
In our system, we broke it down by charging and discharging state. The charging interval consists of the compressor, storage tank, and heat exchanger. The discharging state consisted of another heat exchanger and the air motor and generator. For the testing of the heat exchanger that we are constructing we took advice from the ASME Single Phase Heat Exchangers (PTC 12.5 – 2000) standard. This standard outlines the main concepts and equations that we can use to calculate the efficiency of the heat exchanger. It also goes about outlining the procedures and setup to make sure that we can achieve reliable and accurate results. To test and characterize the 2-stage compressor we used the ASME Performance Test Code on Compressors and Exhausters (PTC 10 – 1997). This code was useful to us because it walked through testing procedures and the creation of testing equipment. It has lots of useful equations and an example calculation for a two-section compressor with an externally piped intercooler between the two stages.
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ASME Standards Collection, https://asmestandardscollection.org/Login.aspx.