THE TOPIC - PEAK LOADING
For architects, mechanical systems can be a black box, especially on large projects. Yes, the basics make sense (supply, exhaust, heating, cooling) but often the details go way over our heads. It doesn’t help that engineers, for good reason, often use complicated acronyms like BTU/h, COP, or Tonnes.
Today’s issue is only concerned with one thing. Peak Loading. What is it? It’s a relatively simple concept. To simplify the idea let’s think about a rope hanging from the roof with a 20lb weight at the end of it. Now let’s add an additional 5lb weight … and SNAP! The rope was designed for a peak load of 20 lbs.
Mechanical systems are the same. Not that they will SNAP under too much load, but both heating and cooling systems are designed for the peak heating and cooling required during the most intense days of the year. (Typically the peak 1% of the year). Think about that 1 day/year where it dips below -20 or above +35. Those are the days that your mechanical system is sized to perform on.
The elephant in the room here is climate change. Yes, buildings are designed to meet peak loads, but those peaks are changing quickly. Even now, most mechanical engineers are designing their systems to perform at a higher peak cooling load than the code requires. The peaks of the 90s are very different from the peaks of the 2030s.
The other problem here is that as we electrify our building stock and cooling demands get higher, the strain on our electricity grid will only increase. And when do they increase the most? You guessed it - during the peak times. That’s why addressing this issue is so important.
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WHAT CAN WE DO
We should look at three areas:
Reducing the peaks
Diminishing the demand
Increasing our efficiency
Let’s dig a little deeper:
1 - Reducing the peaks
The most obvious solution to the peak loading problem is to simply reduce the peaks. This minimizes the need for large mechanical systems and allows for more efficient systems. So let’s get to HOW. The first strategy is simply insulation. Greater levels of insulation reduce the thermal conductivity in the heating and cooling seasons and reduce your need for mechanical intervention. Other passive strategies include exterior shading especially on western and southern faces (in the northern hemisphere) and allowing for passive ventilation to reduce those impacts. There are many other strategies depending on the location, but that’s a start.
2 - Diminishing the demand
Diminishing demand might sound a lot like reducing the peaks, but let’s come at it from a different angle. Reducing demand involves increasing or decreasing the threshold of when mechanical intervention is required. Does your home need to be 21 degrees when it is 35 outside? What if it was 23? Can you put a sweater on for that 1 week of -25 and keep the thermostat at 18? Well reducing those peak demands from a user point of view is an important thing we need to start doing.
3 - Increasing our efficiency
The last item is simply the efficiency of our systems. Unless you’ve had your head under a rock for the last few years you know the value of ASHP’s that can offer upwards of 300% efficiency delivering 3 times the heating as energy input. Well, that’s another way that we need to shave that peak demand as we continue to electrify our grid.
1 PERSON TO FOLLOW
Andy Thomson is an Architect and founder of Thomson Architecture. He posts regularly about energy use in homes, embodied carbon in different building assemblies, and other helpful sustainable strategies. He also has some incredibly helpful tools on his website for EUI & Carbon calculations. Check them out.
1 RESOURCE TO ACT ON
Have you heard of the AIA 2030 commitment? The commitment, which has been signed by more than 1200 firms, is a set of standards and goals for reaching net zero emissions by 2030. Alongside this commitment, they have created the ZERO tool to help you set a target on your project. Check it the ZERO Tool , it’s free!
This is such an important issue that seems to be completely ignored, especially by the “electrify everything” crowd. Peak demand is going to switch from summer to winter, and to meet it,we will need a massive overbuilding of renewables - one study suggests “ All of our building electrification scenarios resulted in substantial increases in winter electrical demand, enough to switch the grid from summer to winter peaking. Meeting this peak with renewables would require a 28× increase in January wind generation, or a 303× increase in January solar, with excess generation in other months. Highly efficient building electrification can shrink this winter peak—requiring 4.5× more generation from wind and 36× more from solar.” Another energy export calls for massive buildouts of hydrogen infrastructure “stored in salt caverns, in pressure vessels, as a liquid in insulated tanks, or as ammonia. It will be moved around, cheaply via pipelines, or at a higher cost by ship, train, or truck. And it will need to be strategically positioned to cover the risk of supply shocks, whether they be the result of normal weather patterns, extreme weather events and natural disasters, conflict, terrorism or any other cause.” All of which can be replaced with efficiency, reducing demand and turning our buildings into thermal batteries.