Definition
Basic
Water heating is a thermodynamic process using an energy source to heat water above its initial temperature. Typical domestic uses of hot water are for cooking, cleaning, bathing, and space heating. In industry, both hot water and the process of water heating to produce steam have many uses also.
Domestically, water is traditionally heated in vessels known as water heaters, kettles or pots. These metal vessels heat a batch of water but do not produce a continual supply of heated water at a preset temperature.
Appliances for providing a constant supply of hot water are variously known as water heaters, hot water heaters, hot water tanks, boilers, heat exchangers, calorifiers, or geysers depending on whether they are heating water in domestic or industrial use.
History
Popular Use
In many countries the most common energy sources for heating water are fossil fuels: natural gas, liquefied petroleum gas, oil, or sometimes solid fuels. These fuels may be consumed directly or by the use of electricity (e.g. A Kettle). Alternative energy such as solar energy and heat pumps, hot water heat recycling, and sometimes geothermal heating, may also be used if available, usually in combination with backup systems supplied by gas, oil or electricity.
One quite popular arrangement where higher flow rates are required is to heat water in a pressure vessel capable of withstanding a hydrostatic pressure close to that of the incoming mains supply. A pressure reducing valve is usually employed to limit the pressure to a safe level for the vessel.
In North America these vessels are known as hot water tanks and may incorporate an electrical resistance heater, an air source heat pump or a gas or oil burner heating the water directly.
Where hot-water space heating boilers are used DHW Cylinders are usually heated indirectly by primary water from the boiler, or by an electric immersion heater (often as backup to the boiler). In the UK these vessels are known as unvented. In the US, when connected to a boiler they are known as indirect-fired water heaters.
Money Involved
Cost
Demand water heaters cost more than conventional storage water heaters. However, you may find that a demand water heater may have lower operating and energy costs, which could offset its higher purchase price.
For Gas and Oil Water Heaters
You need to know the unit cost of fuel by Btu (British thermal unit) or therm
(1 therm = 100,000 Btu).
365 X 41045/EF X Fuel Cost (Btu) = estimated annual cost of operation or
365 X 0.4105/EF X Fuel Cost (therm) = estimated annual cost of operation
Example: A natural gas water heater with an EF of .57 and a fuel cost of $0.00000619/Btu
365 X 41045/.57 X $0.00000619 = $163.
For Electric Water Heaters, Including Heat Pump Units
You need to know or convert the unit cost of electricity by kilowatt-hour (kWh).
365 X 12.03/EF X Electricity Cost by kWh = estimated annual cost of operation.
Example: A heat pump water heater with an EF of 2.0 and a electricity cost of $0.0842/kWh
365 X 12.03/2.0 X $0.0842 = $185.
Production
Types of Water Heating Processes
Warmed/hot water can be produced in a number of different ways:
Immersion Heaters
Water heating by electricity is usually done by an immersion heater mounted in the top of the hot water cylinder. The heater contains an insulated electric resistance heater and a temperature sensor. Domestic immersion heaters (usually rated at 3 kilowatts in the UK) run on the normal domestic electricity supply.
Electric showers and tankless heaters also use a immersion heater shielded or naked which is turned on by the water passing and turned off when the tap is closed. A group of heaters working each one or together provide different heating levels. Electric showers and tankless heaters usually have since 3kilowatts to 7.5 kilowatts according the voltage supply. Industrial immersion heaters (such as those used in electric steam boilers) may be rated at 100 kilowatts, or more, and run on a three phase supply.
Tankless Water Heaters
Tankless Water heaters are also called on-demand water heaters. These provide hot water right where you need it, when you need it, without a storage tank. Using electricity, gas, or propane as a heat source, tankless water heaters, in some cases, can cut your water-heating bill by 10 to 20 percent. The savings come by eliminating standby losses - energy wasted by warmed water sitting around unused in a tank.
Challenges
Present Challenges
Although tankless heaters save on electricity bills, Installing a tankless system comes at an increased cost, particularly in retrofit applications. They tend to be particularly expensive in areas such as the US where they are not dominant, compared to the established tank design.
Tankless heaters are sometimes limited to a choice between CO2 problematic energy sources: gas and electricity. This sometimes makes it difficult to include other heat sources, sometimes including certain renewable energy options. One exception is solar heating, which can be used in conjunction with tankless water heaters. However, tank-type systems have a much wider choice of heat sources available, such as district heating, central heating, geothermal heating, micro CHP and ground-coupled heat exchangers.
Energy Management
The efficiency of a system lies in the hands of the user. If the Combined heat and power system is not managed probably and if proper training is not provided in the installing and maintenance, it will not perform to the specific energy efficient standard, hence, using more energy than required. Therefore, proper training and information must be given to those who are involved in the running of the system and fault detection methods must also be put in place.
Fault Detection and Diagnosis (FDD) aims to recognise and diagnose faults quickly, systematically and automatically before additional damage to the system occurs or before the system fails. It is brought about by using a combination of continuous monitoring and data analysis.
Possibilities
Solar Heating
Over 70% of the average household’s energy use goes into space and water heating, so a source of free hot water to use instead of commercial energy can make a dramatic financial saving.
Solar Water Heating is the renewable technology of choice for most UK households as it offers a quicker payback (7-15 years for an average household) than Photovoltaics (20-30 years) and the advantage that there is already an established network of installers. More immediate financial impact on your energy budget can achieved through energy saving measures such as loft and cavity wall insulation that typically pay for themselves in 1- 3 years.
Solar water heating does require plumbing and heating expertise to size, install and balance effectively, not typically suitable for the DIYer. The last thing you want s to spend a substantial amount of money installing an energy efficient technology within your home and then 3 months down the line, realise that you’re actually spending a lot more due to inefficient plumbing.
Key Countries
Countries with the Most Installed Solar Energy
(in MW)
1. Germany - 9,785
2. Spain - 3,386
3. Japan - 2,633
4. USA - 1,650
5. Italy - 1,176
Prospects
Solar Water Heating
Solar panels can utilize not only direct sunlight but indirect sunlight as well to heat water for your home. They convert the heat in sunlight into heat for water.
Heat Banks
Heat Banks are advanced hot water thermal storage units, providing high flow rates of mains pressure drinkable hot water. The Heat Bank stores Heat Energy which can be utilised to provide domestic hot water. This heat energy is transferred to mains water by a plate heat exchanger. The water within the Heat Bank (stored water) can be heated by various methods, including Gas/Oil Boilers, either directly or indirectly (using a coil), or by Electrical Immersion Heaters utilising various tariffs.
Combined Heat and Power Systems
Combined Heat and Power (CHP) integrate the production of usable heat and power (Electricity), in one single, highly efficient process. Their increased sophistication means that the overall efficiency of CHP plants can reach up to 80% efficiency in comparison to between 35% and 40% for a conventional Plant.
As an energy generation process, CHP is fuel neutral. This means that a CHP process can be applied to both renewable and fossil fuels. The specific technologies employed, and the efficiencies they achieve will vary, but in every situation, combined heat and power offers the capability to make more efficient and effective use of valuable primary energy resources.
CHP generally meets local energy needs; heat, power and increasingly cooling (CCHP, Combined Cooling Heat and Power). It also avoids the unnecessary 8% efficiency losses incurred through the transmission and distribution of electricity through the National grid and local distribution networks.
As CHP units are located on site, it is possible to utilise the heat by-products of electricity generation for heating purposes. This eliminates the unnecessary losses in the distribution network and the wasteful heat release into the environment. The primary energy savings of up to 40% helps not only to conserve resources, but saves the environment with lower.
Transition to Globalisation
Renewable Energy Development: Smaller Projects That Think Big
Petra Solar is attempting to go the way of the utility pole in an effort to ingrain renewable energy into neighborhoods across its home state of New Jersey. And it's doing this by jumping onto the back of those poles, quite literally.
The five-year-old solar company is behind a 40-MW project being installed for PSE&G, the largest utility in New Jersey. There are no solar farms or sprawling rooftop installations, but rather individual 220-watt modules mounted 15 feet up on utility poles across a wide swath of the state.
In all, PSE&G is installing between 180,000 and 200,000 units — one pole at a time — in the 300 towns and cities that the utility serves. The individual modules each feed directly into the grid, and they act as independent units. Together through Petra Solar's software and monitoring network, they form a virtual power plant.
Globalisation > Economy > Energy > Sources > Renewable
Transition to Political Tools
World's Largest PV Solar Park Comes Online in Germany
German officials have opened a 78-megawatt portion of what they say is now the world's largest solar PV Park. Saferay’s 78-MW plant on former open-pit mining areas near Senftenberg in eastern Germany was completed in three months. The plant includes 330,000 crystalline solar modules and 62 central inverter stations.
Political Tools > National > Germany > Dom. Policies > Economy > Energy > Renewable
Transition to Political Actors
The International Solar Energy Society
The Solar World Congress 2011 was held in Kessel, Germany. Approximately 700 participants from over 60 countries were present. The congress demonstrated that a combination of solar and other renewable energies, in combination with energy efficiency and smart storage technologies, can meet our current and future energy needs.
Political Actors > Business > Sustainability
