Director Low carbon Initiative, Professor Heriot-Watt University Edinburgh, UK
The ability to keep buildings, people, goods, food and beverages cold is a vital requirement for many sectors of our global economy.
In the 20th we were able to rely on the miracle of cheap fossil fuel electricity to provide that cold but long before then the cold of the winter months was captured and transported across the seasons, and the oceans, to provide similar services using natural ice, that if well stored could last for months and years. The growing environmental imperatives in the 21st century are making building designers once more turn to this extraordinary substance in the drive for ever more sustainable buildings. Humanity now faces major environmental challenges associated with having more people on the planet, fewer resources per person and a changing climate. These powerful trends are growing in scale, impacts and importance. This article is structured to begin with a brief review with four main environmental drivers on the way in which we currently design and service buildings and concludes that energy storage will be increasingly important in the future, and that ice can be used effectively as the medium for that storage.
21st CENTURY ENVIRONMENTAL DRIVERS ON BUILDING DESIGN
Climate Change – Mitigation. The 4th Report of the United Nations’ International Panel on Climate Change(IPCC, 2007) states that there is now unequivocal evidence that the climate is warming as a result of man-made emissions of greenhouse gases, the chief of which is CO2 . There is now a strong and growing imperative from International and national Governments to act to reduce the impact of climate change on the planet leading to emissions reduction targets introduced by governments, driving the move to Low Carbon Buildings with significant reductions in energy use and carbon emissions.
Climate Change – Adaptation. The increasing frequency and magnitude of extreme weather events across the world is covered daily in the Press. The need grows to sensibly locate buildings that are robust and resilient to resist events such as storms, floods, fires, droughts, heat waves or related collapses of communication and energy infra-structures. Buildings and cities need now to be designed to withstand a more extreme future .
Fossil Fuel depletion: Cost of Energy. Over the last century buildings have tended to use more energy year on year to provide indoor comfort conditions. However, as fossil fuels become scarcer as a result of the Peak Oil phenomenon , the issues of energy cost and security of power supply become more critical. Concerns over the rising cost of energy were amply born out in 2007 when oil prices doubled in a couple of months to over $147 a barrel. It is impossible to predict future prices but it is inevitable that as global supplies diminish, energy prices will rise significantly over time.
Security of energy supplies. The knock-on effects of both less abundant energy supplies and increasingly extreme energy events is the rise of systemic and catastrophic blackouts, brownouts and interruptions of energy supplies. These will require all organisations, and in particular large ones that are technology dependent such as offices, schools, hospitals, factories and universities, to invest more in building or site level micro-grid systems that are reinforced against grid fluctuations and failures to minimise the risk and impacts of energy failures on their operation. Security and stability of energy supply is easier to provide where the energy demands of premises are robust, defended, non-peaky and modest.
The Importance of Energy Storage. Central to providing solutions to all four of the above strong environmental drivers is the need to provide significant levels of energy storage in building to reduce the need for fossil fuel energy, to shift loads across time and to shave peak loads that can detrimentally produce energy spikes in the supply grid that cause local supply collapse, particularly when exacerbated by extreme hot and cold weather spells. A growing challenge, in an age of very ‘peaky’ glass buildings is to generate stable demand profiles demand and supply relationships between buildings and grids. This article deals with the rise and fall and rise again of the use of ice in the cooling systems in buildings.
ICE COOLING IN ANCIENT TIMES
From the dawn of recorded history, men have stored the cold of the winter months to re-use it in the heat of summer in the form of ice . Our forefathers cooled their drinks, food, brows and rooms, by cutting the ice off ponds and rivers, or scraping it from mountain sides, in winter and storing it in underground ice-houses through the spring. Ice-houses have been opened in summer to provide ice for the kitchen and the table for thousands of years. On a Cuneiform tablet sent by an Assyrian governor to his wife Iltani in 1800 BC was written: “Let them unseal the ice of Qatara. The Goddess, you and [your sister] Belassunna drink regularly, and make sure the ice is guarded”. Ice was used thoughout Antiquity by the Greeks and Romans and throughout the Middle East , India and China.
THE ICE COOLED BUILDINGS OF THE 18th AND 19th CENTURIES
The Rocco-Baroque period of architecture is known for its ornate decoration, but it also resulted in some of the most sophisticated ‘passive’ buildings using natural energy flows for heating and cooling. One such building is the Villa Campolietto, in Herculaneum, by the sea, south of Naples . It was laid out in 1775 by Van Vitelli, in a square, with the four corner blocks of apartments divided on the Piano Nobile where the family entertained on the first floor, by a huge cross axis of double-height rooms capped by a large raised rotunda in the centre with windows on four sides creating a venturi tower. Beneath the ground floor are two further basement levels including water cisterns and an ice storage room. Ice was brought down to it from the mountains to the north east. The walls are massive, providing inter-seasonal heat and cold storage capacity, with a plastered tufa construction. The genius of this building is its ventilation systems. In warm weather the whole building could be opened up to catch the wind. In very hot weather the external doors and windows could be shut and the venturi tower of the rotunda above the stairway would draw cooler air up from the basements through the transverse ventilation system. In extreme heat ice from the ice store could have been brought up in boxes to cool individual rooms. In conditions of dire heat basement living areas remained cool with temperatures kept constant by sea breezes blowing over the ice stores.
THE ICE TRADE
Ice was historically widely traded throughout history. The ice stores of the Sultans in Cairo were filled with ice brought by camel trains from the mountains of Lebanon. The ice stores of Granada were filled from mountains hundreds of miles away to the north. By the 18th century the ice trade was a major global economic force. The ice trade had spread to Chile in South America by 1800 where ice was cut from the Andes and lowered on ropes by Indians who then transported it some 90 miles on mule back at a brisk trot (where roads permitted) to Lima, a city that used between 50–55 cwt a day (a hundredweight being about 2.5 metric tonnes). Tschudi, travelling in 1840 claimed that the trade was so important that its interruption might ‘excite popular ferment’ and consequently ‘in all revolutions’ care was taken to avoid commandeering the mules used in the transport of ice. Right up until the 1980s there are reports of natural ice being stored in winter for use in the ‘salad days’ of summer in ice-pits in the Kurdish mountains of Northern Iraq. It may be that adjacent mountain ice-stores could supply cooling ice to cities in the Gulf that suffer blackouts and can find no respite from summer temperatures that increasingly trend to soar over 50 °C, at which temperatures local populations do tend to take to the streets in demonstrations against discomfort. The greatest of all Ice Trades was started in the United States In 1815 Frederic Tudor, the ‘Ice King of Boston’ sent his first shipment of ice from Boston to Martinique in the West Indies to relieve the Yellow Fever Epidemic that raged there (Nagengast, 1999). While this could be considered as a medicinal use of ice to bring down temperatures by its direct application to the body, it was also considered as ‘comfort cooling’ of patients. In 1827 the ice-plough was invented by Nathaniel Wyeth on Lake Wenham near Boston, Massachusetts. The plough was drawn behind horses and enabled large quantities of blocks of clear, pure ice to be cut from the lakes, stored in huge above-ground ice-sheds and then transported by train to the coast where they were loaded onto wooden sailing ships and transported to Latin American, Europe, India and as far as China, where ice allegedly was sold for the price of its weight in silver. Supposedly 50 000 people and thousands of horses worked in the American natural ice industry at it height but by the middle of the middle of the century European ice began to be largely imported from Norway. The first shipment of ice went out from Norway in 1849 when the first Fredrik Olsen took a cargo of ice for the Parr-brothers from Drøbak to Britain on the brig Oscar. Trade was necessarily a two way venture and in Europe the Norwegian trade flourished because the Steam Age had begun and engines needed coal and coal mines need pitprops from timber, and this came from Norway. Steam engines then also pumped water out of the dykes of Holland, and the dykes needed timber. The industrial towns of Europe grew rapidly driving demand for planking for housing. Norway supplied the timber and the planking because steam engines had augmented water driven sawmills. All of this produced saw dust necessary for the isolation of ice transport to Britain and the Continent. Dams were formed near the Norwegian fjords, and Europe was experiencing the little ice age, and therefore production of large ‘crystal’ clear cubes of ice was possible. Ice was often stored in large sheds to keep the ice for the end of season to secure for the highest prices.
The sailing ships were tied up alongside the fjords and slides were made to facilitate the loading down into the ships. The ships had windmills on deck to pump out melt water from the ice on the voyages to the market . The Ice trade was an integral part of the 19th century industrial revolution. Imported American ice became most popular in Britain in the 1840s and the last delivery of imported ice to the Royal ice-houses was as late as 1936. Originally from Lake Wenham, this ‘arctic crystal’ was widely used in Britain where those selling it boasted that they could get a delivery of Wenham ice to any house in Britain within 24 hours. It was gradually replaced by ‘Wenham’ ice from Norway, from where over 300 000 tons a year were imported by the 1890s. The reason why it was preferred to British ice was that it was clear and clean whereas the British ice was often pellucid and polluted.
Three factors are cited as being responsible for end of the ice-houses, and the ice trade, in Europe:
1 World War I took the young men off the land, and made the seas dangerous for those shipping it.
2 The increasing use of the refrigeration.
3 The third reason for the demise of the ice-house was much less obvious. It was because the climate had changed. By the end of the nineteenth century the mean global temperature was rising steadily, heralding the end of the ‘Little Ice Age’.
The significant thermal factor for the ice-house was that although the mean increase in global temperature was relatively small, getting on for c. 0.3°C between 1860 and 1920 (c.1.0 °C between 1860 and 2008), this increase in temperature meant that there were no longer, over time, sufficient cold winters in much of Europe to regularly stock its ice-houses. So the key factor here for a particular ‘Ice’ technology is not how much warmer it gets, but whether the increase in temperature experienced crosses a critical threshold of performance for this particular technology.
The warmer the world gets the more energy it will require to make and store ice artificially and the more carefully we will have to harness this amazing resource.
ICE IN 20th CENTURY COMFORT COOLING
Air conditioning was first used on a large scale at the turn of the 20th century to cool food, but as early as 1748 William Cullen at Glasgow University experimented with evaporating ether under a partial vacuum. It was not until 1805 that Oliver Evans, an American, caused water to freeze using a similar process, and the possibility of cheap cold appeared. At that time many were also experimenting with freezing mixtures and the great natural ice trade was at its peak. In 1834 a closed cycle system was patented by Jacob Perkins, an American working in England, and in the mid-1840s the use of room coolers was pioneered independently in the USA by physician John Gorrie, who used ice to cool air in hospital wards in Florida and Charles Piazzi Smyth, a Scot.
In 1862, at an International Exhibition in London, crowds were amazed to see hot-looking steam apparatus churning out miniature icebergs and one of these machines, made by Seibe (Ferdinand Carre produced the other ice making machine at the exhibition) was bought by the Indian government and sent to relieve the suffering of the troops in India. In the 1870s a few ice production factories were set up in cities and provincial towns but they were expensive and took time to become established. In 1877 a breakthrough was made when meat from England was first exported to America in refrigerated ships, and in the 1960s many cities around the world still got their main ice supply from cold storage plants from which one bought blocks of ice. Fridges were not designed into most European homes until the 1960s. The first recorded proposal for the use of ice in comfort cooling in buildings was by George Knight of Cincinatti who in 1864 proposed a hospital cooling systems in Scientific American featuring a ventilations system in which the fan driven incoming air was cleaned and cooled with sprayed ice chilled water. In 1865 Nathaniel Shaler in next door Newport patented a system where air was blown across ice in holders in a ‘tortuous passage’ . In 1880 New York’s Maddison Square Theatre was using about 4 tons (3630 kg) of ice to cool patrons at each summer evening performance . Fresh air was filtered thought 12m long cheesecloth bags passing over wooden included racks containing 2 tons of ice into ductwork to various openings through which cool air ‘poured in the house to reduce the temperature and to furnish a supply for respiration’. By the 1920s and 1930s ice block cooling systems were used in the USA in Schools, Cinemas and Nagengasht also describes the inventive systems designed to cool the Carnegie Hall in 1889, and the New York Stock Exchange in 1901, both designed by engineer Alfred Wolff, the first great ice cooling system engineer. By this time the use of mechanical ice was beginning to prevail and for the first time ‘enterprises were organised’ to provide central cooling systems, particularly for brewing, printing , textiles, ice making and storage. Comfort cooling was still too expensive at that time and even ice was sparingly used due to its expense at a time when ‘…ice is not very cheap and cold cannot be produced as cheaply as heat’. In large American buildings natural ice cooling systems saw a revival in the late 1920s and 1930s. Money was pumped into marketing the advantages of ice based systems in the States claiming that mechanical systems were still too expensive to make home cooling feasible. The ice industry saw this as an opportunity to sell their cheaper ice but the continuation of the industry depended on persuading the air conditioning manufacturers to design systems that used their natural ice and also that the customers could be persuaded that ice systems were best. In the end none of these conditions were met, lakes were becoming more polluted and ice proved to be a messy, perishable and difficult medium, unlike electricity that was clean, reliable and increasingly cheap. Electrically chilled and humidified air conditioning systems, pioneered by the French began to dominate the industry and it was not for over half a century that ice again was used in large systems.
ICE STORAGE IN 21st CENTURY BUILDINGS
The environmental concerns outlined above have significantly impacted on the way we now design buildings to drastically reduce energy use in them and carbon emissions from them. Architects can seldom be prevailed upon to design climatically intelligent buildings and a generation of ‘glass buildings’ are extremely difficult to heat, cool and manage. Their energy supply and demand profiles exhibit extreme peaks in very hot and very cold weather that in turn destabilize the ability of grid utilities to supply uninterrupted power. We now are seeing the rise again of ice as an important medium in a growing number of HVAC systems. In the historic examples of harvesting, storing, using and transporting ice we saw what a economically valuable commodity it is, how robust and durable it is as a substance and that it has huge negative-energy storage potentials. Today we are experiencing the advent of a new generation of ice cooled buildings with systems that combine the harvesting of natural cold sources in the environment, in the ground and night skies for example, and the efficient provision of top-up freezing mechanically. The building-integrated ice reserves are used to shift energy demand loads across hours to use cheaper off-peak supplies for cooling, with low cost electricity bought when demand charges are low too, if applied at all. Such systems reduce the total energy demands of buildings by shaving the expensive peaks off demand profiles in hot weather.
Most modern ice storage systems are one of two types :
• Direct Ice Production systems using heat exchangers with ice / water on one side and a sub-freezing fluid on the other where ice forms on the evaporator surface of the machine directly. Two such types are the harvester systems, where layers of ice are shed into an open slush tank, and the ice-on-coil systems with external melt.
• Indirect Ice Production systems where a secondary fluid is used and the refrigeration systems cools a brine solution (eg. glycol and water) to sub-freezing temperatures which in turn produces ice on the external surface of a heat exchanger over which the cooling air then passes.
A range of different control strategies are used including :
• Chiller-Priority Controls are the simplest of this form of Thermal Energy Storage (TES) where the chiller runs continuously under conventional chiller control modes, possibly with demand limit, and the remaining cooling capacity is provided by the ice TES.
• Adaptive Optimal Reinforcement Learning Control using the ability of the machine to learn and evolve optimal algorithms to integrate-time dependent costs of electricity into the controls to reduce grid energy consumption and costs while maintaining required temperatures internally. Optimal control outcomes are defined as resulting in maximum operating costs savings in these controls.
Because of the growing need to use effective, low cost, thermal energy storage (TES) in buildings the growth of ice based systems in the last decade has been phenomenal. A growing number of large skyscrapers use ice TES systems to manage extreme electricity demand peaks and save energy . The Bank of America HQ off Time Square in New York houses in the sub-basements in 44 cylindrical ice tanks, roughly 3 meters cubed enough ice to provide 25% of the annual cooling for the building, and 55% of the dirunal load on the hottest days. On hot summer afternoons, when power demand spikes, utilities typically fire up their least efficient and most polluting generators. During these peak periods, 90% of smog-forming particulates are emitted by just 50% of power plants. Since buildings with ice TES do not need to draw on this dirty power, the building’s ice tanks will help to cut out a disproportionate share of pollution, a further benefit of the systems. The ice is produced at night, when excess electricity from the co-generation system is used to produce the ice that is then melted during the day to supplement the cooling system. The Southern California Public Power Authority (SCPPA), working with Ice Energy, have planned distributed energy storage projects to demonstrate savings, such that if put into general use, would reduce fuel consumption by operating utilities by up to 30%, using TES and efficiency “negawatts”, that in some cases cut energy demand by up to 90%. Over two years, the 11 small participating utilities will install 6,000 of the ice TES devices at a total of 1,500 locations, providing 53 megawatts of energy storage to relieve strain on the grid . The units make cheap ice overnight using a high-efficiency compressor to freeze 450 gallons of water (1700 ltires). In the middle of the day, the device shuts off the regular air conditioner for the peak afternoon hours and instead pipes a stream of coolant from the slowly melting block of ice to an evaporator coil installed within the building’s heating, ventilation, and air-conditioning blower system until the entire ice block has melted – which should be sized to take about 6 hours – to cover for the peak afternoon load on the grid.
Ice Energy is a leading provider of advanced ice energy storage and smart grid solutions to the electric utility industry in the USA . Founded in 2003, the company is based in Colorado and has had particular success with its domestic and commercial systems like the ‘Ice Bear’ have been put into many homes and their systems into major national retailers, restaurants and fast-food outlets, convenience stores, data-centres, libraries, fire and police stations, schools, light commercial and manufacturing facilities, municipal buildings, an airport and even a motion picture studio.
We have seen in this article that ice has been used by man to preserve and cool since time immemorial. In the 21st Century the rising price of energy and the need to reduce greenhouse gas emissions, while at the same time withstanding extreme weather conditions and blackouts, will lead to the development of a new generation of ice storage systems for buildings, in machine-made and controlled systems, re-coupled to the ambient cold of the environments around them. The new Ice Age for building is here!