Human-powered balloons

balloon launch oculus

hot air tank

The station is reimagined as a collector of renewable, abundant anthropogenic heat energy — turning the balloons into large-scale, visually powerful symbols of sustainability and creative re-use within Berlin

air heat pumps

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Technology

In–depth study · Human–powered balloons

human—powered balloons

IN–DEPTH STUDY · METABOLIC HEAT AS A RENEWABLE RESOURCE

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The Thesis aims to re–invent the Station of Tears as a Station of Joy — by introducing a Balloon Station where hot air balloons are manufactured and launched into the Berlin skies. As part of the Architectural Technology investigation, and in line with the themes of celebration, joy and re–invention, the currently wasteful practice of filling balloons with hot air using vast quantities of non–renewable propane is questioned — with an assumption that a contemporary, renewable, urban and ‘fun’ source of energy can be found instead.

Unlike the standard practice of launching balloons in remote areas where no source of heat other than the propane is immediate available, the launch of balloons in an urban environment has the advantage of utilising fixed structures capable of supplying heat from a number of energy sources. In Victorian times, the success and reduced cost of ballooning was very much caused by the availability of coal gas within cities — entrepreneurial balloonists such as Charles Green negotiated deals with the London Gas Company allowing them to power balloons by using the expansive city mains02. Today, the use of polluting coal gas is obviously out of question, however the principle of utilising energy available as a by–product of the urban activity is equally applicable.

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This concept of harvesting by–product, ‘waste’ heat has been brilliantly demonstrated by a series of paraSITE homeless shelters, by the Chicago artist Michael Rakowitz. The custom–made inflatable structures hook onto the building HVAC exhaust systems to provide warm, temporary shelters — and simultaneously send a powerful message to the city.

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Thermal images of a typical balloon launch.

The propane burner produces heat up to 100°C — this energy is wasted when the ­b alloon is deflated. www.ballonflug.com/ thermografie.php 02.

Richard Holmes: Falling Upwards, page 57 03.

Glaisher and Coxwell launch their ­­­­­h igh– altitude balloon from the gasworks, 1862 04.

ParaSITE for Joe H. near Battery Park City in Manhattan 05.

ParaSITE for Michael M. that complies with the anti–tent law by being less than 3.5 feet in height

‘Hooking onto’ the increasingly energy–efficient HVAC systems is impractical considering the volume of the balloons — so other sources of anthropogenic (man–made) heat have to be found in the city — luckily, there is a whole variety of

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such sources at busy transport intersections. Considering that transport links and related activities are essential to the performance of the city, and happen all year round, the anthropogenic heat in transport nodes can be seen as a constant source of renewable energy. The balloons are then large–scale, visually powerful symbols of sustainability and creative re–use within a city. Considering the optimism with which Germany has embraced the principle of alternative energy, the idea of creating a device to celebrate this new

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era seems most appropriate — especially if it’s by means of something as positive and ‘fun’ as hot air balloons. The following study examines the feasibility and the application of anthropogenic heat at a transport node in order to launch hot air balloons into Berlin’s skies.

The balloons are then large–scale, visually powerful symbols of sustainability and creative re–use within a city

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In–depth study · Human–powered balloons

Technology

SIMILAR APPLICATIONS In order to understand the viability of the idea in principle, a series of similar applications are analysed:

WASTE HEAT FROM LONDON TUBE HELPS HEAT 1200 HOMES In November 2013, an announcement was made01. about a “first–of–its–kind” project aiming to capture waste heat from a vent of the London Tube’s Northern Line to reduce the heating load of an innovative energy network in Islington.

The pilot project is a partnership between Islington Council, the Mayor of London Boris Johnson, UK Power Networks and Transport for London, alongside European Union’s CELSIUS project. The project aims to cut up to 500t of CO2 emissions per year02., and is part of London Mayor’s initiative to localise energy production, with further plans and possibilities outlined in the Buro Happold–produced ‘Secondary Heat’ report03.. In the report, heat from the Tube carries a small weight in plans for powering London as a whole, yet is praised for being available “in concetrated quantities which makes it easier to recover”04..

There are no news since the announcement; the fact the waste heat is injected into an existing, mixed–source network of 1200 homes makes the efficiency difficult to evaluate, however the initiative shows that potential of transport-generated energy sources is already recognised.

PARIS METRO REDUCES HEATING FOR SEVENTEEN APARTMENTS In 2010, Paris Habitat announced a tender05. for a system of heat exchangers to draw energy from a nearby Rambuteau Métro station which has a constant temperature of 14—20°C throughout the year. An old stairwell is key to keeping construction costs low, the use of water pipes and under– floor heating are suggested.

The small scale of the application, and the limited data mean little further analysis is possible.

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CHURCH TO BE KEPT WARM BY BERLIN SUBWAY AIR In November 2013 06., a pastor of the St Paul church in Wedding, Berlin filed a planning request to BVG regarding the use of heat exchangers to extract energy from the warm 01. www.celsiuscity. eu/2013/11/15/wasteheat-from-the-tube-willhelp-to-warm-hundredsof-homes accessed 28–01–2015 02. www.power-technology.com/features/ feature-extracting-heatfrom-the-tube-london-­ transport accessed 28–01–2015

air of the nearby Pankstraße Metro Station in order to make his church “carbon–neutral”. This resulted in an ongoing dispute regarding the ownership of the subway tunnel space and the arrangement of the services, made more complex by the unwillingness of all the parties to cooperate.

This project highlights the potential of heat extraction from the subway in Berlin, and the complexity that is involved in realising such projects in areas of multiple ownership.

03. www.london.gov.uk/ priorities/environment/ tackling-climate-change/ energy-supply accessed 28–01–2015 04.

Buro Happold: London’s Zero Carbon Energy Resouce ‘Secondary Heat’ Summary Report, July 2013, page 12 05. www.renewablesinternational.net/paris-mtrohelps-heat-low-incomehousing/150/537/28907 accessed 28–01–2015 06. www.tagesspiegel.de/ berlin/bezirke/wedding/ wedding-jetzt/u-bahnheizung-fuer-weddinger-kirche-heisseluft-fuer-schinkelskirche/9041270.html accessed 28–01–2015 07. www.bbc.com/news/ business-12137680 accessed 28–01–2015 08. www.content.time. com/time/health/article/0,8599,1981919,00. html accessed 28–01–2015

BODY HEAT FROM STOCKHOLM STATION MOVED TO NEIGHBOUR BUILDING The body heat of the 250 000 daily users of the Stockholm Central Station is used to reduce the heading loads of a neighbouring 13–storey office building by 15–30%07.. The heat generated by the commuters is captured by the station’s ventilation system and used to warm water in underground tanks, from where the energy travels over 90 meters to the new office building. The total system costs around £20 000 and is expected to pay for itself quickly08.; this is also a first test of what the designers hope can become common practice in the increasingly expensive energy market.

This project in the only one currently in operation, and successfully demonstrates the potential of capturing low–grade waste heat source energy and its further transportation — the effect of the collected energy on the heating load of a large office block shows that large quantities of energy are available, and that large–scale application is possible with reasonable costs.

Considering the apparent novelty of the idea and the site–specific nature of the installation, little universally applicable data is available — however, the precedents do show the possibility of extracting heat from mass–transport hubs — as such, the Study will proceed with calculation–based speculations.

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In–depth study · Human–powered balloons

Technology

There is a great multitude of anthropogenic heat sources in the Friedrichstraße station: transport, fast–food kitchens on ground floor, mechanical servicing equipment, escalators, lights and signage, human body heat etc — yet without a period of extensive & elaborate measurements and following data simulation (which is impossible for this study) this overall picture would be difficult to comprehend fully. The complexity would be further increased if factors like passive solar gain, heat radiated from neighbouring office buildings, varying heat loss etc were taken into account.

In light of this, a simplified model of calculations based on human body heat is used with the assumption that if this low–grade heat source can generate enough energy to power several balloons, the idea is viable in principle — and that the rest of the anthropogenic heat sources will ‘cancel out’ any heat loss, if not add to the amount of energy available in the station.

50 000 people pass through the Friedrichstraße station daily01. Assuming that an average person spends 10 minutes at the station 50 000 x 10 = 500 000 min = 8 333 human hours are spent in the station daily.

To find out how much ‘body heat’ the 50 000 people generate in the station daily, the metabolic rates of the activities in which they engage have to be considered:

Sleeping

83 W

Seating, relaxed

104 W

Standing at rest

126 W

Standing, light activity (shopping etc)

167 W

Walking on level, 2km/h

198 W

Standing, medium activity (shop assistant)

209W

Walking on level, 5km/h

360 W

Bicycling, 15km/h

418 W

Running, 15km/h

990 W

The two primary activities in the station include waiting for the transport or shopping, and walking from one location to another — therefore the corresponding metabolic rates of 167W and 360W have been chosen from the table above, and their average used for further calculations: (167 + 360) / 2 = 263.5 W is the average metabolic rate of activity in the station.

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The basic relationship between energy, time and power is as follows: Energy = Power x Time To calculate the amount of energy generated by 50 000 people in the station daily, the average metabolic rate or ‘power’ found above is multiplied with the amont of human hours spent in the station every day: Energy = 263.5W x 8333h = 2 195 745.5 W·h = 2 196 kW·h of ‘free’ energy is generated by the users of the station daily.

While kilowatt–hour (kW·h) is the unit of energy commonly used for measuring electrical energy, the International Standard SI unit of energy is the Joule — which is more useful when calculating balloon lift as specified in the question.

One kilowatt–hour equals 3600kJ, which means that 2 196 x 3600 = 7 905 000 kJ is available daily to convert to heating air for balloons.

01. invidis.de/2009/10/ u-bahnhof-friedrichstrase-total-digital accessed 26–01–2015 left, table.

TheEngineeringToolBox. com/­m et–metabolic– rate–d_733.html accessed 26–01–2015 03.

Thermal image by ­Perception ­E nhancement Studios titled ‘Rush Hour’

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In other words, a 10–minute (600 second) visit of the station by one person with the calculated metabolic rate generates only 600s x 263.5W = 158.1 kJ of energy, yet when multiplied by 50 000 this amounts to an impressive 7 905 000 kJ

The station is reimagined as a collector of sustainable, abundant, easy–to–understand and ‘fun’ energy from an unexpected source

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In–depth study · Human–powered balloons

Technology

To calculate how much energy is required to ‘power’ a hot air balloon, a popular 100 000 cubic foot (2 832m3) balloon01. capable of carrying up to 5 people is used for the basis of the calculations.

The weight of the entire balloon system is broken down as follows: 2832 m3 nylon & Hyperlast envelope

101.5 kg

passenger basket

63.5 kg

double burner

22.5 kg

3x20 gallon (75.7liter) propane tanks

183.5 kg

5 average passengers

62 x 5 = 310 kg02.

Sub–total (net):

681 kg

2832m3 of air heated at 99°C

2686 kg

Total (gross):

3367 kg

The hot air balloon operates due to the air inside the envelope being lighter than the surrounding (ambient) air. The balloon floats when the balloon system and the heated air inside weigh less than the surrounding air displaced by the balloon — resulting in the exertion of buoyant force. The difference in the air weights is the gross lift, the difference minus the weight of the system (here, 681kg) is the net lift.

The net lift of a hot air balloon at a given flight altitude is calculated as follows03: TA = TG — [0.0065 x (A — EG)] P = 1013.25 x [1 — (0.0065 x A)/288.16] L = 0.3484 x V x P x [(1/[TA + 273.16]) — (1/[TI + 273.16])] where A = maximum planned flight altitude in m EG = elevation of take-off site above sea level in m L = total lift of the balloon in kg P = air pressure at maximum planned flight altitude in hPa TA = ambient temperature at flight altitude in °C TG = ambient temperature at take-off site elevation in °C TI = average internal envelope temperature in °C V = envelope volume in m3 04.

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The formula demonstrates that one of the main factors affecting the amount of lift is the difference between the average internal and the ambient temperatures — the hotter the day, the more energy is required to power the balloon. In case of this study, the hotter the day, the more energy will also be produced by the people sweating in the station — so rather than the amount of energy, the maximum ‘cap’ for lift depends on the maximum allowable internal temperature of the balloon — which is limited to 120°C05.

The maximum limit of 120°C is imposed to protect the fabric of the balloon from degrading too quickly — the nylon itself does not start to melt until around 230°C; in fact the internal temperature is based on the average anyway — the actual internal distribution of air at different temperatures is seen in thermal image overleaf.

For the purposes of the study, the required minimum temperature to create lift will be calculated — to eliminate energy waste and to prolong the life of the nylon fabric.

To estimate the performance of the balloon on an average day in Berlin, the average 01.

Such as the Cameron Concept C–100 balloon

yearly temperature06. of 11°C is used (TG); the maximum planned flight altitude of

02.

Sarah C Walpole ‘The weight of nations: an estimation of adult human biomass’, 2012

of the building at 35m is used, resulting in EG = 70m. The first calculation (shown)

03.

Cameron Balloons: Hot Air Balloon Flight Manual, issue 10 page 89

1000m is used (A); and the elevation of site above sea level at 35m plus the height uses the average internal temperature of the envelope at 99°C — just below the maximum 100°C recommended by Cameron Balloons.

Applying the numbers above to the formulas shown earlier results in the following:

04. www.ballonflug.com/ thermografie.php 05.

US Department of Transportation: Federal Aviation Administration Certificate data sheet 06. www.climatevo.com/ berlin,de data for 2014

TA = 11 — [0.0065 x (1000 — 70)] = 5 °C P = 1013.25 x [1 — (0.0065 x 1000)/288.16] = 990.4 hPa L = 0.3484 x 2832 x 990.4 x [(1/[5 + 273.16]) — (1/[99 + 273.16])] = 887.33 kg

The resulting net lift of 887.33 kg is significantly larger than the 681 kg weight of the balloon system, which means that heating the air inside the balloon to 99°C will result in it shooting up into the sky on the average 11°C Berlin day.

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Technology

In–depth study · Human–powered balloons

Considering that in the previous calculation, the net lift of the balloon was significantly larger than the weight of the balloon system, the internal temperature of 99°C is wasteful when applied on the average 11°C day in Berlin. The balloon lift formulas from above are then re–arranged to find out the internal air temperature that is required to achieve equilibrium at specific ambient air temperatures in Berlin; all the knowns and constants from the previous calculation are replaced with numbers so that only TG, the ambient temperature at take-off site, and TI, the internal temperature of the balloon, remain.

The original formulas: TA = TG — [0.0065 x (A — EG)] P = 1013.25 x [1 — (0.0065 x A)/288.16] L = 0.3484 x V x P x [(1/[TA + 273.16]) — (1/[TI + 273.16])] Formulas with constant/ known parameters plugged in: TA = TG — 6 P = 990.4 hPa 681 = 0.3484 x 2832 x 990.4 x [(1/[(TG — 6) + 273.16]) — (1/[TI + 273.16])] Expanded further: 681 = 977196.78 / (TG + 267.16) — 977196.78 / (TI + 273.16) TI = 977196.78 / [977196.78/(TG + 267.16) — 681] — 273.16 A range of ambient temperatures at take–off level (TG) is then tested to determine how hot the air inside the balloon’s envelope has to be to achieve equilibrium; slightly higher temperatures are required for take–off. The resulting ambient / internal temperatures, based on weather data from 201401., are seen in the table:

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Ambient, T G

Internal, T I

Coldest day

— 12°C

> 51°C

Average winter temperature

3°C

> 60°C

Average yearly temperature

11°C

> 72°C

Average summer temperature

17.5°C

> 82°C

Hottest day

31°C

> 103°C (< max. 120°C)

The values in this table are used to determine how much energy is required to heat the air from the ambient temperature to that required for equilibrium; slightly more energy will be required for take–off. This relationship is calculated as follows: Q = Cp x m x dT where Q = amount of heat required in kJ Cp = specific heat of air in kJ/kg · K m = mass of air in kg dT = temperature difference in K To calculate the mass of air, the volume of the balloon envelope at 2832m3 is multiplied with the density of air at that temperature. Temperature differences are calculated from the previous table, air data is taken from the table below02.:

01. www.climatevo.com/ berlin,de data for 2014 02. www.EngineeringToolBox.com/air– properties–d_156.html

Air temp.

Density, p

Specific heat, C P

51°C

1.109kg/m3

1.005 kJ/kg·K

60°C

1.060kg/m3

1.009 kJ/kg·K

72°C

1.029kg/m3

1.009 kJ/kg·K

82°C

0.996kg/m3

1.009 kJ/kg·K

103°C

0.9461kg/m3

1.009 kJ/kg·K

The energy required to power the balloon on the day with the average ambient temperature is calculated as follows: Q = 1.009 x (2832 x 1.029) x [(72 + 273.15) — (11 + 273.15)] = 179 361.66 kJ

To find out how many times this energy can be generated by the metabolic heat of the station users, this number is compared to 7 905 000 kJ from the respective step: 7 905 000 kJ / 179 361.66 kJ = 44 balloons (!!!)

The same set of calculations is applied to the other, non–average, temperatures: on the coldest day 39 balloons can be launched; in winter 45 balloons can be launched; in summer it’s 43 balloons, and on the hottest day 40!

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In–depth study · Human–powered balloons

Technology

The calculations above show that there is an abundant amount of metabolic heat within the station — enough to power 44 balloons in one day. To successfully capture this low–grade heat dispersed in the station air, however, a coherent set of technological and strategical decisions are required.

TECHNOLOGY A series of strategically placed air heat pumps of the highest efficiency can capture a large proportion of the energy contained within the (normally disposed of) exhaust air of the station and the subway. The standard benefits of air heat pumps transferring energy from external ambient air are multiplied when heat is extracted from the warmer exhaust air of the station.

An air–to–air heat pump system is proposed, where 1. the exhaust air of the station is passed through the ‘external’ heat exchange coils 2. the anthropogenic energy carried by the exhaust air is absorbed by a refrigerant 3. the boiling, gasified refrigerant is compressed by a pump to increase its temperature 4. the refrigerant passes through a pressure valve into ‘internal’ heat exchange coils 5. the gasified refrigerant condenses back into a liquid, transfers the heat to indoor air 6. the liquified, cool refrigerant returns to the ‘external’ coils to start its new cycle 7. the hot indoor air is stored in a large insulated tank until its use is required In addition to providing hot air for the balloons, this system can be used in junction with a heat recovery ventilation system of the building, resulting in a shared and more efficient infrastructure.

APPLICATION To achieve maximum efficiency, the heat pumps are proposed in locations with the highest concentration of warm air — at subway exhaust vents, at retail unit clusters, at the top of the station vault where the proposal creates a controlled ventilation gap.

The use of air heat pumps at the locations above addresses two issues at once: provides energy for the launch of the balloons / the building, and simultaneously reduces the amount of energy currently required to ventilate those high–use areas.

Finally, the air source system is significantly simpler to introduce in such a dense urban area — compared to the ground source heat pump, the installation and resulting disruption have a minimal impact on the daily life of this busy transport node.

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Arseni Timofejev www.arsenit.com

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