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Water heating

technology Maturity 11-13 Next article →

We use hot water for many important jobs every day. It helps us cook meals and keep our homes clean. We also need it for warm baths and to heat our living spaces.

Water Heater White
Water Heater White

To make water hot, we must move heat into it. This is called heat transfer. This process uses an energy source to raise the water temperature.

Ancient Water Heater
Ancient Water Heater

In the past, people used metal vessels like kettles, pots, or cauldrons. These tools heated a batch of water but could not provide a steady supply.

Most homes today use a storage water heater to keep water ready.

FEMA - 63 - Photograph by Dave Saville taken on 10-04-1999 in North Carolina
FEMA - 63 - Photograph by Dave Saville taken on 10-04-1999 in North Carolina

This is a cylindrical tank that holds water continuously. In North America, these tanks often hold between 75 and 400 liters. They can use electricity, natural gas, or even solar energy. Natural gas is very popular in the US because it is often cheap. The tank stays hot by using a burner or an electric heater. However, heat can slowly leak through the tank walls over time.

Boiler and Cylinder
Boiler and Cylinder

There is another way to get hot water called tankless heating.

Water heater bathroom
Water heater bathroom

These are also called instantaneous or on-demand water heaters. They do not store much water inside the machine. Instead, they heat the water right as it flows through a coil. Many of these use copper because copper is great at moving heat. This method provides a steady, continuous flow of hot water. A major downside is that these systems can cost more to buy. A study in Minnesota showed a long payback period for them.

Some people use solar energy to heat their water.

solar heater dsc00632
solar heater dsc00632

Solar collectors are placed on roofs or walls to catch sunlight. One way is the direct-gain type, where water goes straight into the collector. Another way is a closed-loop system. In a closed-loop system, a special fluid carries the heat to the water.

Flat-plate solar thermal collector, viewed from roof-level
Flat-plate solar thermal collector, viewed from roof-level

This protects the system from freezing. Solar heating is very common in places like Cyprus and Israel. In those countries, 90 percent of homes use solar water heating.

Water heating works in many different ways around the world.

ModCon boiler system
ModCon boiler system

In big cities in Scandinavia, Finland, and Poland, they use district heating. This system sends hot water from large plants to many homes at once. In tropical places like Singapore, people use much smaller tanks. These tanks might only hold 10 to 35 liters. This is because the air and water are already quite warm. Whether using a big tank or a small solar panel, we find clever ways to stay warm.

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🖼️ Images & Media (13)
File:Active Indirect Water Heater Diagram.svg
Active Indirect Water Heater Diagram.svg
File:Water Heater White.jpg
Water Heater White.jpg
File:FEMA - 63 - Photograph by Dave Saville taken on 10-04-1999 in North Carolina.jpg
FEMA - 63 - Photograph by Dave Saville...
File:Boiler and Cylinder.jpg
Boiler and Cylinder.jpg
File:Water heater bathroom.JPG
Water heater bathroom.JPG
File:solar heater dsc00632.jpg
solar heater dsc00632.jpg
File:Flat-plate solar thermal collector, viewed from roof-level.png
Flat-plate solar thermal collector,...
File:Ancient Water Heater.jpg
Ancient Water Heater.jpg
File:Kerosene water heater, 1917.jpg
Kerosene water heater, 1917.jpg
File:ModCon boiler system.jpg
ModCon boiler system.jpg
File:WH safety valve.JPG
WH safety valve.JPG
File:Scaldburn.jpg
Scaldburn.jpg

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