What Volume Does a 1 m Change in Water Level Represent in the Golden Falls Lake?

Golden Falls lake. Image courtesy Google Maps, Airbus and Maxtar Techmologies

Distance can easily be measured on Google Maps on desktop by right clicking and selecting "Measure distance" from the context menu. Then simply click the start point and the end point, or draw a series of line segments by repeatedly left clicking and following an outline until the end point is reached. This is useful for measuring distances, but you may not have known that it's also possible to measure area by drawing a series of line segments around for instance a field, and then clicking on the start point again. You can read a complete article I wrote about how to do this here.

I'm curious about how much volume the Golden Falls compensatory lake can hold and what 1 m of level actually equates to in terms of volume. Calculating this is relatively simple, by determining the area of the lake in square metres and multiplying by 1 m. It's not totally accurate obviously because of the sloped sides of the lake, and area increases as water rises. Also the apparent area of the lake might  be somewhat larger than when this satellite image was taken sometime last year. However, I roughly measured the area of the lake as explained above, using the "beaches" as a guideline, to get a ball park figure. 

From the map above, area is approximately 256,000 square metres. 

A cubic metre is simply a cube with sides 1 m long.

So multiply area in square metres by height in metres to give volume:

Volume =  256,000 x 1 = 256,000 cubic metres

Cubic metres are usually written using the SI symbol for length, "m" with a superscript "3" meaning it's cubed.  (SI comes from the French Système international d'unités)

So volume = 256,000 m³ 

The ESB have been discharging 35 m³ of water per second from the dam in the last couple of days. Multiplying flow per second by the number of seconds in a day, this works out at:

35 x 60 x 60 x 24 =  3,024,000 m³

Under normal circumstances that would drop the lake level by:

3,0240,000 / 256,000 = 11.8 m approx

However, flow into the lake from the Poulaphouca dam is reducing this drop in level. Currently, stats aren't available for flow rates from the Poulaphouca dam. However, knowing average daily flow discharges from the Golden Falls dam from ESB stats and the discrepancy between drop in headrace level at Golden Falls and what it should actually be, it should be relatively straightforward to calculate a value for flow.

Types of Plastics Used in the Home: How to Identify PVC, PET, Polythene and Others.

© Eugene Brennan

What Are Plastics?

"Plastic" is a term applied to any material that can be moulded or bent into shape; for instance, soft toffee, modelling clay, or red-hot iron is plastic because it can be reshaped. In general though, when we speak of plastic, we mean polymers or synthetic materials made from petrochemicals.

There are at least 10 different types of plastics used in the home, the type used depending on the application. Many of these plastics can be recycled and are marked with a symbol and numeric code indicating the plastic type.

Types of Plastic Used Around the Home

There are lots of different types of plastics used in and about the home. The most common ones are:

1. Polyethylene (Polythene)
2. Poly Vinyl Chloride (PVC), also known as vinyl
3. Polypropylene
4. Polystyrene
5. Polytetrafluoroethylene (Teflon)
6. Nylon
7. Polyesters, polyethylene terephthalate (PET) being the most common
8. Acrylic
9. Polycarbonate
10. Polyurethane

Note: These numbers are not the plastic ID codes. See the information about each plastic below for codes.

What Is Plastic Used For?

Well virtually everything! From the '60s onwards, plastic began to replace or supplement many items which were traditionally made from materials such as metal, wood, glass, stone, ceramic and natural textiles. Some examples:

• Textiles: Cotton, wool, silk, linen and hemp were the original textiles used from ancient times. We now have acrylic, polyester and nylon.
• Footwear: Shoes originally had leather uppers and soles. PVC is now used for trainers, and soles are made from PVC or polyurethane foam.
• Windows and doors: Originally made from timber, they are now also made from PVC.
• Food storage, eating and drinking utensils and bottles: They were originally ceramic, glass or metal but are now also made from polyester, polypropylene and polyethylene (Polythene.)
• Electrical insulation: Originally rubber, now also PVC.
• Furniture: Plastics such as polystyrene are used for stackable, hard seating. Padded seating coverings are often made from PVC or "vinyl," and soft, flexible, polyurethane foam forms the internal padding.
• Car and machine parts: Many parts in cars were made from metals such as steel, brass, aluminium alloy and rubber. These are now often replaced by plastics such as PVC, nylon, ABS and polystyrene.
• Casings of electronic/electrical devices and appliances: Originally made from wood, metal or Bakelite, they are now generally made from polystyrene, polypropylene or ABS.
• Fixtures and fittings in homes: Lighting, electrical fittings and conduit and bathroom fittings.
• Plumbing: PVC, PEX (cross-linked high-density polyethylene), polybutylene and CPVC are extensively used for domestic plumbing, drainage pipes, water distribution mains to homes, gas distribution and protective conduit for underground electrical cables.

Why Is Plastic Used So Much?

• It's cheap and made from a relatively inexpensive raw material.
• It's relatively strong and can be used for many applications.
• Many plastics are inert, so they can be used in contact with solvents, acids and alkalis, water and other chemicals without suffering any ill effects.
• Unlike organic materials such as wood and natural textiles, plastic doesn't decay when exposed to wet or damp conditions for long periods.
• Thermoplastics can be moulded into lots of different shapes using an industrial process called injection moulding (basically forcing soft plastic into a mould under high pressure). So no machining is necessary, as is the case with metals. Plastics can also easily be 3D printed.
• Plastics can be easily coloured.
• Nylon, a tough and durable type of plastic, can be used for moving parts in machinery without the requirement of lubrication (it has a relatively low coefficient of friction like Teflon.)
• Plastic is a non conductor of electricity, so it can be used as an insulator in electrical appliances.
• Many plastics can be easily recycled by being melted down or shredded to make new products.
• As a synthetic fibre, it can be more durable than natural fibres when made into textiles.
• Many plastics are good thermal insulators, so they are used as handles on kitchen utensils, tools, saucepan lids etc.

What Are the Disadvantages of Plastic?

• Unlike scrap metals, for instance—which are more valuable—plastic is such a ubiquitous and cheap material that there has been very little incentive to recycle it until recent decades. So it ends up in landfills and as litter.
• For some applications, plastics cannot be used because they lack the strength of metals. Composite materials such as carbon fibre (a fibre reinforced polymer) will eventually become more widely used.
• While plastic parts are often used in machines and tools, they aren't as tough or durable as metal, so plastic parts can wear or break more easily.
• Ultra Violet (UV) exposure from sunlight can cause plastics to crack and degrade over time unless special additives are added to the material during manufacture.
• There are concerns about carcinogens used as fillers or trapped monomers leaching out of plastics used in food storage containers and drinking vessels.
• It can't be used for applications where it is exposed to very high temperatures.
• Microbeads less than 1mm diameter used in personal care products as an abrasive pose an environmental hazard and may harm aquatic animals.

What Are the Two Main Categories of Plastics?

Plastics can be broadly divided into thermoplastic and thermosetting types.

Thermosets are heated during manufacture, and a non-reversible chemical reaction takes place. Once they have cooled and set, they stay solid and can't be re-heated and re-moulded, e.g. for recycling. Examples are Bakelite, urea formaldehyde and vulcanisation of rubber.

Thermoplastics can be reheated repeatedly without undergoing any chemical change. This allows them to be reshaped or recycled into new materials. Examples are PVC, polyethylene and polypropylene.

What Is Plastic Made Of?

There are several stages in the manufacture of plastic, but it all starts with crude oil and natural gas. There are three main stages:

• Stage 1: Crude oil (petroleum) and natural gas are extracted from ground.

• Stage 2: Intermediate products known as petrochemicals are made from crude oil and natural gas.

• Stage 3: Polymerisation and other chemical processes are used to produce plastics from petrochemicals.

Stage 1: Crude Oil and Natural Gas, the Raw Materials for Plastic

The raw material for most plastics is crude oil, also known as petroleum. This is a thick black, brown, yellowish or greenish liquid extracted from the ground using oil wells on land or at sea. Crude oil was formed when creatures and plants such as zooplankton and algae died and settled to the bottom of the ocean. Over millions of years, sand, shells and other stuff collected on top of them. As a result of heat and pressure, this organic material was transformed into oil.

Crude oil is a complex mix or soup of lots of chemicals and must be refined. Oil refineries are large industrial complexes which process thousands of barrels of oil daily. In a refinery the oil is cleaned of contaminates such as salt water. Several processes are then used to break the oil up into its constituent components, typical of which is fractional distillation. In this process, oil is heated, and various compounds boil off at different temperatures and can be separated. This results in distillates such as petrol (gasoline), kerosene, lubricating oil, wax and bitumen. Petrochemicals such as benzene, toulene and xylene or BTX are also produced here.

Natural gas is also used as a raw material. This is processed at a natural gas processing plant into a variety of different types of gases.

Diagram depicting the how petrochemical plant feedstocks are obtained. CC by SA 3.0 Unported via Wikimedia Commons

Petrochemicals are the intermediate chemicals in the production of plastics. Typical petrochemicals are ethylene, propylene, benzene, butadeine, toulene, and xylene. Petrochemicals are produced in petroleum refineries, natural gas processing plants and by a process known as cracking.

Stage 3: Polymerisation

In this process, the petrochemical monomer raw product is converted into a long chain polymer or plastic. A typical petrochemical is ethylene gas with the formula C₂H₄. In the polymerisation process, an activator known as a catalyst speeds up the chemical reaction. Lots of ethylene molecules join together into chains to form a polymer.

Polymerisation of ethylene to form polyethylene. © Eugene Brennan

How to Identify Plastic Type

Most plastic products or their component parts are marked with a resin identification code (RIC) symbol, also known as a plastic identification code (PIC) specifying the type. This is also sometimes called a recycling code, however this is technically incorrect as not all these plastics are recyclable. This allows ease of identification for recycling purposes.

Plastic resin identification code (RIC) embossed onto the underside of a medicine bottle. © Eugene Brennan

Resin Identification Code (RIC) for polyester. © Eugene Brennan

Polyester

There are many polyesters, but the most common type encountered in the home is PETE or Polyethylene terephthalate. PETE is spun into a synthetic fibre which is used to produce textiles. Polyester fibre is also mixed with natural fibres such as cotton to improve durability.

Uses

• Shirts, trousers, coats and other clothing, sometimes under the brand name "Terylene"
• Bed sheets
• Plastic bottles
• Tarpaulins
• Insulating tapes
• Upholstery
• Insulation in clothing and as padding in duvets, pillows etc

Products Made From PET

© Eugene Brennan

Hi-vis vest. © Eugene Brennan

Plastic bottles. © Eugene Brennan

Resin Identification Code (RIC) for polyethylene. © Eugene Brennan

Polyethylene

High density polyethylene (also known as polythene), has a high strength to weight ratio and also a high resistance to solvents, acids, and other chemicals.

Uses

• Plastic bags
• Storage containers for food and other products
• Beverage bottles
• Toiletry bottles
• Fuel tanks on vehicles and garden/yard power equipment
• Containers for household cleaning chemicals
• Petrol (gasoline) storage containers
• Storage containers for motor oil
• Blow moulded cases for tools

Products Made From HDPE

Plastic power tool case. © Eugene Brennan

Plastic bottles. © Eugene Brennan

Safety helmet. © Eugene Brennan

Resin Identification Code (RIC) for PVC. © Eugene Brennan

Poly Vinyl Chloride (PVC)

Poly Vinyl Chloride is more commonly known by the abbreviation PVC or "vinyl." It comes in two forms rigid or flexible. The rigid form is used for structural work such as door and window frames and the frame members of plastic greenhouses. The flexible form is widely used as electrical insulation, upholstery coverings, and inflatable products.

Uses

• Doors, windows, and greenhouse frames
• Upholstery covering, chair seat coverings
• Beach balls, footballs and other inflatable products
• Fascia and soffit
• Downpipes and gutters
• Waste and water pipe
• Insulation for electrical wire
• Electrical conduit
• "Vinyl" records

Products Made From PVC

Gutters and downpipe. © Eugene Brennan

Waste pipe. © Eugene Brennan

PVC window. © Eugene Brennan

Fascia and soffit. © Eugene Brennan

Electrical conduit and saddle clip. © Eugene Brennan

Insulation on electric cable. © Eugene Brennan

Resin Identification Code (RIC) for low-density polyethylene. © Eugene Brennan

Low Density Polyethylene (LDPE)

Low Density Polyethylene is a soft flexible plastic widely used for making clear plastic bags and sheeting. It has a higher resilience than HDPE, which basically means that it can be stretched or deformed more without cracking or ripping. You can tell the difference between an LDPE and HDPE bag by scrunching them up. HDPE bags make lots of crackly noise. It is also ideal for snap-on lids, as it can deform and seal around the rim of the container.

Uses

• Plastic bags
• Clear, flexible plastic sheeting, e.g., for polytunnels
• Soft, flexible snap on lids
• Shrink wrap (cling film)
• Waterproof linings of cardboard juice and milk cartons

Products Made From LDPE

Soft plastic bag. © Eugene Brennan

Resin Identification Code (RIC) for polypropylene. © Eugene Brennan

Polypropylene

Polypropylene is a tough, flexible plastic and used for applications which require these properties. It also resistant to fatigue, which means that it can be repeatedly deformed or strained without cracking. PP also has good resistance to acids and solvents. Polypropylene is able to withstand higher temperatures than HDPE, and so is used for applications where a product must be sterilised or heated, e,g. kettles and dishwasher proof kitchenware. It is also used for containers which contain dairy products such as butter, as it can withstand the heat given off by products during industrial filling processes.

A disadvantage of PP is that it degrades when exposed to heat and UV present in sunlight, so additives must be used if products are required to be long lasting in sunshine.

Uses

• Beverage bottles
• Dish washer proof plates and food storage containers
• Living hinges on lids
• Food storage containers
• Dairy product containers
• Toiletry bottles
• Ropes
• Coal sacks
• Ratchet straps (tie-down straps for holding loads during transport)

Products Made From Polypropylene

Lids on jars. © Eugene Brennan

Butter spread container. © Eugene Brennan

Flower pot. © Eugene Brennan

Rope. © Eugene Brennan

Ratchet strap. © Eugene Brennan

Coal sack. © Eugene Brennan

Pringles lid. © Eugene Brennan

Resin Identification Code (RIC) for polystyrene. © Eugene Brennan

Polystyrene

Polystyrene has two main advantages. It is a stiff and rigid polymer, and unlike other plastics which are translucent or opaque, polystyrene can be made clear. So it is ideal for applications which require these characteristics such as CD and display cases.

Uses

• CD cases and display boxes
• Casings for kitchen appliances, TVs and Radios, torches and other electrical gadgets
• Seed trays
• Blister packing
• Disposable cutlery
• Disposable ballpoint pens
• Expanded polystyrene (Styrofoam) is used as insulation, as a packing material and for disposable cups.

Products Made From Polystyrene

Measuring jug. © Eugene Brennan

CD case. © Eugene Brennan

Seedling tray. © Eugene Brennan

Ballpoint pen casing. © Eugene Brennan

Resin Identification Code (RIC) for other plastics. © Eugene Brennan

Other Plastics Used in the Home

Several polymers which don't have their own specific recycling number are classed under category seven as "other plastics." Not all of these are recyclable.

• Nylon - Tough and durable and used for ladies tights, sports clothing and moving parts in machines.
• Polycarbonate - This is tough and durable and can be bent and deformed to a large extent without cracking. It is used for making sunglasses, safety glasses, CDs and as synthetic "glass" in greenhouses.
• Acrylonitrile butadiene styrene (ABS) - Another tough plastic with high impact resistance. It is used for making Lego bricks, carrying cases, electrical boxes and computer monitor and printer cases.
• Urea formaldehyde - Commonly used for sockets, plugs, switches and other electrical fittings.
• Polyurethane - Used in foam form as a padding in cushions and upholstery, air filters on lawn mower engines and as packing. Some air and fuel lines are made from this material. Hard foam soles on footwear are also polyurethane-based.
• Polytetrafluoroethylene (PTFE) - This plastic has a very low friction coefficient, i.e., it is "slippy." It is known by the brand name Teflon as the non-stick coating on cooking utensils. It is also used in tape form for sealing the threads on plumbing joints.
• Polymethyl methacrylate (PMMA) or Acrylic - Used as a synthetic fibre in sweaters and as clear sheeting or pipe under the trade names "Perspex," "Plexiglas," "Acrylite," and "Lucite."
• Nitrile rubber - One of the many types of synthetic rubbers. These are used for a variety of products, including gloves, o-rings, sealants, fuel lines and water hoses in vehicles, wellingtons and anything which requires a flexible, waterproof material.

Products Made From Other Plastics

Nylon strimmer (string trimmer) line. © Eugene Brennan

Nylon tights. © Eugene Brennan

Nylon gears in a clock mechanism. © Eugene Brennan

Urea-formaldehyde electrical fittings. © Eugene Brennan

Polycarbonate safety glasses. © Eugene Brennan

Polycarbonate CD. © Eugene Brennan

PTFE plumber's tape. © Eugene Brennan

Polyurethane foam air filter. © Eugene Brennan

Nitrile rubber O-ring. © Eugene Brennan

Older Plastics Used in the Home:

• Bakelite - This is a thermosetting plastic used in the past for electrical fittings, electrical insulation, door knobs and saucepan handles. Because it is a thermoset, it doesn't melt or deform when subjected to high temperatures.

• Celluloid - Used for making dolls, musical instruments, pens, table tennis balls, cutlery handles and as a veneer for clocks and furniture

Bakelite plug. © Eugene Brennan

Bakelite door knob. © Eugene Brennan

Celluloid knife handle. © Eugene Brennan

Recyclable Plastics

Not all plastics are recyclable, but it depends on region and country. Soft plastic made from low and high density polyethylene, expanded polystyrene packing, and hard polystyrene casings (such as plastic bags and film) are generally not accepted by waste collection service providers. Expanded polystyrene needs to be compacted, and the cost of building large compactors is high.

PET, HDPE, and PP (used in bottles, lids, food trays and containers) are generally recyclable.

What Products Are Made From Recycled Plastic?

According to the World Wildlife Foundation (WWF), eight million tons of plastic globally is dumped into our oceans. There are limitations on what can be made from recycled plastic, but typical products are:

• trash bags
• washing machine outer tubs
• garden furniture
• planters
• mats and rugs
• footwear

Plastics in the Ocean: What Are Microplastics?

Tiny microbeads less than 1mm diameter made from polyethylene, polypropylene and polystyrene are used as an abrasive ingredient in personal care products such as skin exfoliating creams and toothpaste. These materials end up in waste water and pass through sewage treatment plants unhindered, and then get carried via rivers to our oceans. These pose an environmental hazard and may harm aquatic animals.

Plastic items in our home and from land based industry and fishing activity also degrade over time, and the tiny fragments eventually end up in the ocean. Larger items such as plastic bottles, floats from fishing nets, items lost or disposed of overboard from ships also pollute the seas.

Let Me Know Your Thoughts!

Was the information in this article useful and instructive? If there you have any suggestions for improvement or any questions, please provide some feedback below. Thanks!

Disclaimer 

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2014 Eugene Brennan

Earth Speeding Through the Universe and How is Speed Measured in Spacecraft

AI image generated by ChatGPT

Did you know that we're travelling at 600,000 km/hr on planet Earth as our home galaxy, the Milky Way, orbits the Local Group, a group of neighbouring galaxies? That's somewhat faster than the mere 1000 km/hr velocity of a point on the island of Ireland, due to the Earth turning on its axis. We don't experience the effects of constant velocity on our bodies, only acceleration and deceleration. So we can't tell whether we're stationary or moving. In space, there aren't any wheels on the ground or axles that can be used to determine velocity by measuring how fast they turn (in older cars, there was simply a cable connected between the driveshaft and speedometer). Aircraft use pitot tubes mounted in the fuselage, with an orifice at the end of the tube exposed to moving air. As air flows over the hole, pressure drops in the tube and this can be converted into a velocity measurement. Spacecraft don't have this luxury because there's no air in space, and instead uses accelerometers. These measure acceleration and deceleration. A process known as dead reckoning can then be employed to determine velocity (by integrating acceleration, knowing how long that acceleration acted for) and distance travelled (by integrating velocity, knowing how long the velocity lasted). Ancient mariners also used dead reckoning to determine their position in the ocean by regularly measuring a vessel’s speed in knots and its direction using a compass.

Golden Falls Headrace Level Up a Metre, Flywheels, Capacitors and Air Compressor Tanks

Image courtesy the ESB

Even with the large discharges from the golden Falls dam, the level in the lake has risen a metre in the last two days. This would be due to significant discharges from the Poulaphouca dam. I'm not sure what the max allowed level is for the lake. I'll see if I can find out. Both the Golden Falls and Poulaphouca lakes act as buffers to smooth out flow. In fact they're analogous to three types of systems, both mechanical and electrical: an air compressor tank, a flywheel on a machine such as an engine or punching machine and the filter capacitors in a DC power supply. In signal theory, all these systems act as low pass filters, storing energy and smoothing out "bumps", converting pulses into smooth ripples—ideally small ripples. If the ripples are too big in an electrical power supply, you get mains hum, which you may have heard in a bad PA system. Back to the lakes, they act as buffers. Once they fill, they no longer smooth out the bumps and the full flow of the River Liffey upstream of Poulaphouca feeds through the system.

Image courtesy ESB.