Awaiting my first semester at university, the hours were long and relaxed. There was little to do but walk, read, think and blog – how lovely!
(Netflix, Youtube and amazing data plans were yet to be a thing thing).
I drank a kopi-o-kosong: black coffee, no milk, no sugar.
My mind was ablaze!
Strolling home in wide-eyed wonder, my imagination rippled in euphoria. The road beside me infinitely folded in on itself like a scene from Inception… in my imagination. Poor cars. Other mental acrobatics ensued on my 30-minute walk home.
A few weeks later, after more cups and reflections on this powerful drug, I posted this:
Those rules were promptly broken, and here I am after 8 years of coffee consistency.
After exploring the experiences of Michael Pollan, I’m inspired to take a break to understand my relationship with this plant.
For a month.
I’ve started today, and the fog definitely settled in at work in the morning. I still feel very much myself, but just about conked out after lunchtime. Work had to go on, and I experienced a second wave of wakeful focus around 4pm!
As the days go by, I’ll be documenting my experience here.
I’m looking forward to weeks of better sleep and rediscovering my mind off coffee. Here we go!
In this moment, 30 trillion of your cells are metabolising, transforming nutrients into energy. This happens even when you sleep, and keeps us alive.
As your cells metabolise, they release heat!
Fun Biology FactBut a Bit Too Much Information
This heat is an inevitable byproduct of the chemical breakdown of ATP (Adenosine Triphosphate), a compound that is your body’s ‘currency of energy’. It’s needed to drive your muscle contractions, move your cells, circulate blood and even get your nerve impulses going!
In the world of aircon, one of the popular ways to measure this heat is with the BTU, The British Thermal Unit.
An indoor aircon unit with 18000 BTU capacity is able to remove 18000BTU of heat (and humidity).
How much heat needs removing from your home?
Let’s start with the internal heat sources. These typically mean energy-consuming things, like appliances, lights and people.
1: Identify the heat sources inside your home
The first major heat source in your home is you!
That’s right – when you sleep, your body emanates about 18 satays of heat energy!
And as you read this, little oranges of heat are radiating from your body. (The healthy choice)
This heat leaves your body by convection and conduction from your skin to the air, which is only possible when the air is colder than your skin. This is usually the case!
Here’s a screenshot of my skin temperature ranging between 33.4 and 33.8°C , taken with this sensor I have!
During a heat wave when the surrounding air is hotter than your skin, the body actually gains heat from conduction and convection – here it can only cool itself down by the evaporation of sweat. Because humidity limits this evaporation, heat loss becomes super difficult! This is why hot, humid climates (like Singapore) are considered much less comfortable than hot climates which are dry. (Like UAE, or certain parts of Australia!)
Other than humans, electrical and cookingequipment are a source of heat gain too. Studies from ASHRAE have been done to determine the recommended heat gain for a variety of these!
But it’s much simpler to assume that 100% of your appliances eventually convert electricity into heat gain.
Fun Facts about Entropy – Why All Your Electricity Becomes Heat
You might think that the light energy, the sound, and the processing power that appliances produce refutes this assumption. But light bounces around your walls until its radiation is absorbed by all surfaces in a room (some escapes out the window). Sound reverberates through the air and surfaces of your house, agitating the molecules which exert friction on each other as heat! In computers, the computation performed in CPUs are simply resistance to the circuit. They perform no energy storage and do no work – simply producing heat as electricity cascades through the billions of transistors to perform instructions.
For the laptop I’m typing this post on, that means 65W!
That means my laptop is emanating about 221.8 BTU/hour, or two plain pratas of heat during the day. Yum.
This leads us to the final table of internal and external loads!
The story doesnt end here!
The heat your house expends today may change over time, which would be wise to consider.
3. Changes over Time
Consider the changes to the number (and size) of people in your home over time.
If you want to minimize the number of times you upgrade/change air conditioning units, it’s a good idea to size for the future. Most air conditioning units last 15-20 years!
Within this time horizon, how will the loads in your house change? Should you size for the largest heat load in the next 20 years? Or the load your aircon serves 80-90% of the time? It might be tempting to just buy the biggest air conditioner you can, but over-sizing your unit can be tremendously wasteful depending on the part-load efficiency.
We’ll cover that… next semester!
I hope this post helped you understand what BTUs are and how the inside and outside of your house matters when you are looking for the right size of air conditioning!
Tracking my data is part of a path to find the minimum conditions I need to be in comfort.
That aside, let’s get to the products!
(Fun fact: Humans have been getting cooler, one of the reasons being less chronic inflammatory conditions over the past bunch of centuries. Woohoo!)
As these products are not your usual smartphone or watch, I’ll be briefly going through their underlying technology first before going through the experience of using it. Feel free to skip those bits if you wish!
The Embr Wave
With Singapore’s intense heat and furious use of aircon, the idea of bringing cooling direct to our bodies was something worth a ($300+) try to me. Exciting new powers of personalized air-conditioning would make sweatingonthewaytowork a figment of the past. I would be so cool.Ha.
So the Wave doesn’t really do that!
How it Works:
The Wave contains a peltier plate, which becomes cool on one side and hot on the other side when you pass an electric current through it.
This is called thermoelectric cooling – it’s a super-cool effect which we use for regulating the temperature of scientific devices and other tiny electronics.
To reject the heat on the other side, peltier plates are often combined with heat sinks (Metal blocks with a lot of ridged parts on them for more surface area) to dissipate this heat away. This explains the wiggly lines on the Embr Wave’s surface! The higher surface area is helpful to more efficiently dissipate heat when being used in Cooling mode.
Does it actually cool you?
Sssssorta. It’s the kind of cooling you would expect on a hot day when you dip your hands into cold water. Or suddenly touch a cold, metal doorknob.
On heating mode, it’s like when you’re in a cold room and cup your hands around a warm mug of coffee.
This pulse of cooling or heating is applied to the underside of your wrist, which has a solid amount of bloodflow and is very thermally sensitive.
The pulse of cold doesn’t remain constant – it comes in waves! According to Embr, this maximizes the feeling you get from each pulse, which I can verify. Having a constant source of cold on your skin tends to be forgotten – receiving waves makes them feel ‘new’ every time.
The Embr Wave comes with a pretty great app, which is where you can set these custom modes for yourself!
Overall, the psychological effect of cold hits slowly over time – I ‘feel’ it more keenly after an extended session with the Wave (like 30-60mins). It’s not exactly the aircon-everywhere I was hoping for, but could be valuable to someone looking for that last squeeze of comfort in a space that is always slightly too hot or cold.
The design is a little blocky for laptop use, as it sticks out the bottom of your wrist! This results in occassional collisions which is not so nice. Also, the Wave 1 is charged by micro-USB (the horror!), but Embr is nice enough to include a cable in the box.
Nonetheless, Embr Labs just recently released an Embr Wave 2 in April, with a sleeker design and, according to them, stronger cooling.
The GreenTEG CORE sensor
The CORE is super cool!
So I was walking to the mall in the BLAZING hot sun one day (normal in Singapore these days, the weather’s been nuts!) and wondered the following:
Would I sweat sooner if I walked slowly in this blazing heat, thereby spending a longer time under the skin-melting gaze of Sauron, on my way to get some KFC?
Or would I sweat sooner if I ran to my dearsweet KFC, thereby spending a shorter duration under the sun, but spending more metabolic energy to do so?
I needed some way to track my core temperature and skin temperature in real time, and graph this against my activity level. It would not be feasible to walk with a thermometer in my mouth. I didn’t have a thermometer pill.
Before investing the remainder of my life into starting a company to research and make such a method + app to track data of such method in realtime, luckily I found out about the GreenTEG CORE!
So you strap this little thing onto your chest, and it senses your skin temperature and their proprietary heat flux sensor to back-calculate your body’s core temperature to a ±0.26°C accuracy. Then it streams this real-time to an APP, which you can LOOK AT in REAL TIME. It was exactly what I wanted!
How it Works
GreenTEG uses a combination of skin temperature, heartbeat and their own research-based algorithms to generate a core temperature that hasgiven super close results to pill thermometers. The CORE is enabled with two algorithms – one incorporating heartrate (Sports Activity Algorithm) and one without (Everyday Living Algorithm). As changes in core temperature do not immediately reach the skin, the Sports Activity Algorithm takes in heartbeat data to come up with a more accurate and immediate figure for core temperature, needed by athletes who require immediate feedback for their sport!
So I got the heartrate sensor too!
For those who find this uncomfortable, the CORE comes with one-day-use adhesive pads too!
As the CORE is relatively simple in function (clip+strap), it’s really all about the app!
While the CORE app doesn’t allow a direct CSV download (yet?) unless you pay a fee for a Research Mode or a Garmin device, you’ll be able to track and set alerts when your core temperature goes off the charts. Here’s me at high activity:
And another steep ramp-up:
And here’s the effect of a sudden heartrate drop:
As you can see, the body takes a while to return back to the normal core temperature of about 37°C!
While I love the functionality and will be saving the detailed analysis for another post, I do wish I could see both graphs on the same creen to observe the timings! Another gripe would be that the app sometimes resets the tracking when the bluetooth connection is lost, but GreenTEG continues to push over-the-air updates to improve this over time (this is why you get the app-enabled tech)
The FOCI Wearable
It’s a little clippy thing that goes on your waist, pushed against your diaphragm to track your breathing patterns! The FOCI was a strange little find on kickstarter, when I was looking for something nondescript to track my breathing patterns over the course of a day!
How does it work?
The FOCI tracks tiny breathing movements and translates this into a predicted cognitive state with the ‘neuro-respiratory patterns’ identified by their AI model. These states are broken down into Focused, Calm, Stressed, Fatigued, Distracted and Flow.
The FOCI is 10g, super lightweight and easy to clip on without noticing, and easily hideable. However, as it can’t get a clear signal while you move around, the only accurate readings come from when you are seated.
While my personal use with the FOCI has been quite brief, so far I’ve found that it quite accurately tracks whether I am in focus or not! While the little bubble moves with your breath, making it fun to look at and track your breathing state, I’ve also found that the best way to maintain focus is to not look at it while you’re tracking yourself.
Overall, while I am interested to see where TinyLogics takes the app and device (graph my breathing please!)
That’s all for the Embr Wave, the CORE and the FOCI! You can comment or subscribe if you like this, or let me know if you’d like to know more about these cool tools!
I’ll do another big review when I gather more interesting tech! (Reon Pocket, I’m looking at you.)
For the engineers and techs in the energy & sustainability sector, I am here for you.
This is your bread and butter!
And I hope to draw it for you with uncommon beauty.
What is a Chiller Plant?
So.. air conditioning takes up about 50% of energy consumption in our commercial buildings.
The cold is costly!
The energy which powers Air Conditioning simply moves machines that throw human heat outside of a building.
This sounds simple, but actually involves a long chain of machines, passing the heat to each other.
This magical process works mainly because of one principle:
Hot things transfer heat to cold things.
In a building, this happens a few times:
Your muscles and organs (37°C) heat your skin (36°C) in your body.
Your skin (36°C) heats the supply air (18°C) from your air-conditioning, making return air (28°C).
The return air (28°C) heats a chilled water supply (7°C) in the aircon unit to a chilled water return (12°C) .
The chilled water (12°C) heats a very cold refrigerant (5°C) in the chiller’s evaporator, to 6°C.
The refrigerant is compressed (6°C -> 50°C) into a high pressure vapor in the chiller’s compressor.
The hot refrigerant (50°C) heats condenser water (30°C) in the chiller’s condenser to 35°C.
The condenser water (35°C) heats the ambient air (29°C) in the cooling tower…
… which is where all our heat goes! The ambient. The sky. The outside.
Is this bad for the environment?
Technically, without air conditioning, we would walk around heating the air anyway.
What these machines do is essentially increasing the gradient between hot and cold.
That’s no problem, right?
The thing is, not all machines are efficient – they produce their own heat while working.
And the energy they consume from power plants.. requires more heat to generate too! Ideally, 100% of the electricity we supply to machines is converted into the useful work we use the machines for. However, some of this heat is inevitably converted to heat and sound produced by friction between mechanical parts and electrical resistance.
The more machinery we run to operate an air-conditioning system, the more heat is generated in the world. Sounds kinda funny, but we don’t really feel the effects of this when we’re chilling indoors!
On to the machines themselves!
1. The Air Cycle (Air Handling Units)
Humans do stuff. Their muscles and organs get warm, and this heat is transferred to their skin, which is transferred to the air around their skin.
This hot membrane of air transfers heat all over the air! Hotter air particles have more kinetic energy, and jiggle faster than their cold neighbouring particles. These hotter particles rise above their inactive neighbours who remain relatively still (AKA Meritocracy). At the ceiling of a room, a fan sucks in these hotties, blowing them past a very cold chilled water coil inside an Air Handling Unit(AHU). This coil’s water is at about 7°C. That’s cold!
The hot jiggly particles collide against this coil, losing their jiggliness to the coil surface. The cold water inside the coil takes gets heated from 7°C to 12°C. Meanwhile, the air is cooled from ~28°C to about 18°C. The resulting average room temperature is somewhere around 24°C, which is the temperature your thermostat tries to maintain.
The cycle repeats. Cold air hits human, human heats air, hot air heats water, hot air becomes cold. Ugga bugga.
2. The Water Loop
Chilled water just took some heat, and needs to drop it quickly. It flows through the Chilled Water Return pipes to the chiller plant, where it will be cooled back to 7°C again, by the chiller.
Chillers have a simple function – Make chilled water cold again.
They do this by passing the 12°C water through super-cold refrigerantfluid, which is about 5°C in the evaporator.
After the 12°C water transfers its heat to the refrigerant, it leaves the chiller at 7°C, on its merry way back to the AHUs.
3. The Refrigerant Loop
Air passed heat to water. Water passed heat to refrigerant. Refrigerants are fluids with ideal properties for containing and releasing energy rapidly, but I’ll be skipping those details for now (low boiling temperature! Rapid phase-change material!),but in summary is a fluid that can be very cold at room temperature. This enables it to be the ‘colder thing’ which the already-very-cold 12°C water can give its heat to.
Once the refrigerant takes this heat, it is compressed into a hot, high-pressure vapor, which enables it to now be the ‘hot thing’ to transfer heat to another water loop, the condensor water loop.
The whole operation of a chiller looks like this:
Which I hope makes sense of this!
4. The Condenser Water Loop – Throwing it all out
In the chiller’s condenser, hot refrigerant now passes its heat to water (Yes, a separate circuit). This water goes to a cooling tower, those huge grilled-boxes you see on top of many buildings in Singapore.
Cooling towers do exactly what you do to cool soup – blow air over it. The hot water is trickled down the serrated walls of metal, and air is sucked through these walls by a huge fan in the centre of the box’s ceiling.
The water that collects at the bottom is at about outdoor temperature, where it is pumped back to the chiller to be heated again.
This stage is called Heat Rejection, the final stage of any air conditioning cycle. It is where the heat of hundreds of warm humans is amalgamated and tossed back out into the air, where it is more easily forgotten.
Is this all necessary?
We’ve all suffered the heat here – air-con definitely makes it feel better. While I don’t have air-conditioning at home, I seem to survive quite well with fans. Even a cool breeze outdoors on a sunny day makes me feel comfortable enough to forget the humidity.
I’m not so sure what the best way is – what do you think?
Note: I excluded the bulk pricing (e.g. 3 cookies for $3.50 = $1.17 per subway cookie) for neatness this time, but also because the bulk pricing doesn’t change the winners in all my categories here. Nonetheless, I’ll share em at the end of this post for ya ref.
Cheapest Chocolate Chip Cookie by mass per dollar: Marks & Spencer!
Heaviest Chocolate Chip Cookie: 12 Cupcakes (maintaining da spot!)
Densest Chocolate Chip Cookie: Jewel (beating Ben’s, now in 2nd place)
What about taste?
With taste being so subjective, I’ve left it out of this comparison – cold data only for the fairest stats. Still, if I had to lend my opinion, I’d break down taste into densityand flavour.
If you love cold, dense, chewy cookies like me, I’d recommend the Starbucks cookie and the Jewel cookie – they’re tied for a pretty great bite density.
For flavour, I hate to say it, but Famous Amos takes the cake for my fave amongst the lot. They’re pretty pricey, and chewy cookies are not their main product, but there is surely some mastery in the ingredients they’ve put in that dough. It’s worth mentioning that Folks & Stories’ brown butter and PPP Coffee’s Marou chocolate chips make for interesting flavours too, if you’re looking for something a little different than the average cookie.
While we’re on subjective thingies, I will say that PPP Coffee had some very chio browning on their cookie. Paired with the large size and unique flavour, this is probably the one you’d wanna get a date or something (I swear I am not sponsored). Check this chioness out:
Hope you found this useful! Lemme know if you think there’s:
Anything I can add to this (obsession)
Anything I coulda done better
Anything I missed out!
You can lemme know in the comments, I’d love the feedback.
I thought it would help to do a cookie comparison to find the best chocolate chip cookie for your buck. Sparked by a friend who sent me cookies from someplace new (Iamnotsponsoredhor), I bought some of my usual chocolate chip cookies to make a big cookie comparison. Here’s the list of chocolate chip cookie contenders:
Folks and Stories
Let’s start with their Dimensions.
12 Cupcakes has the biggest chocolate chip cookie of the lot, with Folks & Stories has the teeniest at 7.6cm (about the length of a namecard)! However, this wouldn’t be complete without thickness:
As suspected, Folks & Stories makes up for its smaller diameter by having the thickest chocolate chip cookie of the lot!
Note: Given their list of unconventional cookie flavours, Folks & Stories doesn’t seem to have a “Chocolate Chip Cookie” per se. I picked their Milk & Dark Chocolate cookie (which they name “N°1 SALT OF THE EARTH”) for this comparison.
Weight (Actually Mass)
Subwayyyyy – 46g
Starbucks – 101g
12 Cupcakes – 116g
Ben’s Cookies – 76g
Folks and Stories – 53g
As expected, the Subway cookies are lightest of the lot, but it’s more than justified by their price!
Chocolate Chip Cookie Comparison Table
I compiled the stats in this table to find the densest cookie of them all and the worthiest cookie of them all.
Cheapest Individual Chocolate Chip Cookie: Subway (for both bulk and non-bulk pricing!)
Cheapest Chocolate Chip Cookie by mass per dollar: 12 Cupcakes (also for all pricing!)
I was surprised to find that 12 Cupcakes had the cheapest chocolate chip cookies per gram, even though I consider them on the pricey side. I would say that if you don’t need so much bulk in one cookie, and just enjoy cookies, I’d get the three cookies from Subway for $3.50 and munch away (tip: they’re cheaper in universities at student price!)
Why Chocolate Chip Cookies?
There are so many flavours out there, but I feel that the classic chocolate chip cookie is the best representation of cookie dough and toppings coming together without distracting each other too much. For instance, double-chocolate cookies are more like a judgement of chocolate than anything else, and peanut butter cookies are overwhelmed by the pure taste of peanut butter. Chocolate chip cookies have little bursts of chocolate, but just enough that the dough itself can shine. I love em.
What about taste?
I wanted to use objective data for this cookie comparison! Everyone has their own preference for what the best part of a cookie’s taste is. For me, I’m particularly a fan of dense bites and complex flavours. I gotta say, the Starbucks chocolate chip cookie has my favourite bite density of them all, while I would pick the Folks & Stories chocolate chip cookie for flavour – I think it’s the browned butter that gives it an edge!
Of course the cheapest way of getting your chocolate chip cookie fix, if you weigh out all the ingredients and prices and divide them out per cookie, is baking yourself a batch at home. I’m a big fan of this article by J. Kenji López-Alt, where he breaks down all the effects of each ingredient on the outcome of a great chocolate chip cookie. I think I’ll share my recipe in another post.
Hope you found this useful! Comment to suggest any other comparisons you’d like to see!