Case Report: Parallel Session on Energy Conservation/CO2

The Solar Heating of Water Regulations in Jerusalem - Energy Saving

by Ariel Cohen, Vice Mayor of Jerusalem

Jerusalem process a unique climate on earth in the sense that it has the highest value of annual sunshine hours among the cities with similar or higher normal rainfall (about 500 mm/y), as well as the highest normal rainfall among stations with an abundance of over 3400 hours annually (on the average) of solar station.

This characteristic of having copious amounts of solar radiation as in subtropical deserts (but still have enough rainfall from desert on semi-arid conditions), is well used for collecting solar energy for water heating.

According to HoughtonÕs Tables in Climatology the average annual number of sunshine hours in the city of Jerusalem is 3473h. This value is particularly high due to its position on a mountain 750 m high and on the desert border.

The Judean desert has only about 100 m annual rainfall and is just 20 km away from Jerusalem.

In order to encourage the citizens of Israel in general and the citizens of Jerusalem in particular, to install solar heating systems, using its unique weather, the following regulations are applied (see detailed regulations at the end):

Since the regulation applies only to new building, the city of Jerusalem is encouraging its citizens to use solar energy applying an amendment (since 1991) to the Land Law as follows: As a result of the above-mentioned regulations, it was found that 57% of 101,000 apartments surveyed in Jerusalem in 1995 were using water heated by solar energy.

Jerusalem has the highest increase in the yearly installation rate of solar energy collectors and solar boilers. As a result, it is expected that it will reach the country average of 69% (!) within the next few years.

We note that out of 1,266,000 households surveyed in Israel in 1995, 872,274 are using solar heating systems. However, in the cities of Haifa and Tel-Aviv the percentages are also somewhat lower (54.6%, and 58.9%, correspondingly) than the country average.

Some additional regulations are also applied to increase the use of solar energy. Such regulations are:

It is proposed that it shall be mandatory to adopt summer time every year in Israel, as is customary in the civilized countries of the world, for a period of at least 150 days. Summer time leads to a saving in energy, by allowing a longer time for activity by daylight and in relatively cool hours, and it adds to the comfort and convenience of the public. The dates between which summer time will be adopted shall be determined by the Minister of the Interior, in co-ordination with the Knesset Committee for the Interior and Environment. In order to increase certainty and to enable proper advance planning, it is proposed that the determination shall be made from time to time for a period og at least three years in advance.

In order to save energy thermal sealing in buildings is also regulated:

The thermal sealing of elements of the exterior of residential buildings is planned and executed according to special Israel Standards.

Also, for example, the characteristics of the thermal sealing of exterior walls of buildings which are not residential buildings are not less than those of a wall built of hollow blocks with a width of 20 centimetres, which is plastered on both sides.

Finally, we include the complete set of regulations, mentioned above, used in Jerusalem for a water heating system heated by solar energy:

  1. No building in which there is a system or installation for supplying hot water shall be built unless the system or the installation is a solar installation.
  2. In a solar installation according to this section, the daily heat output of the collectors shall not be less -
    1. if the building is designed to be used as a hotel, guest house, home for the elderly, boarding school, educational institution or for similar purposes -than 30 kilocalories for each litre of hot water consumption per day on an open system, and than 34 kilocalories for each litre of hot water consumption per day on a closed system;
    2. if the building is designed for residential purpose - than 41 kilocalories per day for each litre of storage tank capacity on an open system, and than 46 kilocalories per day for each litre of storage tank capacity on a closed system or on an open system with a horizontal storage tank.
  3. In a building designed for residential purposes which has a solar installation installed:
    1. The heat transfer capability of the heat exchanger in a closed system shall be at least 1.5 watts per 1 degree centigrade for each litre of the storage tank capacity;
    2. A residential unit in which an open system is installed shall be treated as stated above;
    3. Each residential unit shall have one storage tank of its own.
Storage tank and collector in a residential building
  1. A storage tank and collector in a residential building shall be subject to the special provisions in this section.
  2. The capacity of a storage tank is a solar installation shall be:
    1. For each residential unit with one room - at least 60 litres;
    2. For each residential unit with two or three rooms - at least 120 litres;
    3. For each residential unit with four rooms or more - at least 150 litres;
  3. The following provisions, relating to storage tanks and collectors on the roof of a building, shall be carried out to the satisfaction of the local committee:
    1. The tank and the collector shall not be an eyesore;
    2. The tanks shall be located on a building or buildings so that they fit in architecturally with the whole building;
    3. The colour of the storage tank shall be white, unless the local committee determines otherwise/
  1. In a solar installation a back-up system shall be installed in order to supply energy to heat water in cases where the solar radiation source is not sufficient for this purpose.
  2. The back-up system shall have the capability to heat the water in the storage tank to the temperature of 50 C.
  3. The central heating system may be used as a backup system.

Fujisawa/Saarbrücken/Bangkok/Gulu Municipalities/Luisville and Jefferson County/Ratnapura/Jerusalem/Portland/La Ceiba/Shenyang